Piigp 

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TECHNICAL    GAS-ANALYSIS 


TECHNICAL 
GAS-ANALYSIS 


BY 


GEORGE  LUNGE,   PH.D.,   DR.ING.   (H.C.) 

EMERITUS  PROFESSOR  OF  TECHNICAL  CHEMISTRY   AT   THE   FEDERAL 
POLYTECHNIC   UNIVERSITY,   ZURICH 


NEW    YORK 

D.   VAN    NOSTRAND    COMPANY 

TWENTY-FIVE    PARK    PLACE 

1914 


&- 


Engineering 
Libraif" 


;iO    ,Vm 


PREFACE 

IN  1885  the  Author  published  an  English  translation  of 
Clemens  Winkler's  Anleitung  zur  chemischen  Untersuchung  der 
Industrie-Case,  under  the  title :  Handbook  of  Technical  Gas 
Analysis,  and  in  1902  a  second  edition  of  that  book.  In  both 
cases  he  had  made  a  few  remarks  and  additions  of  his  own, 
but  in  the  main  the  book  was,  what  it  purported  to  be,  a 
translation  of  the  book  of  his  friend,  Professor  Winkler,  who 
died  in  1904. 

During  the  twelve  years  succeeding  the  second  edition  of  the 
Handbook,  the  methods  of  Technical  Gas-Analysis  have  been 
the  subject  of  numerous  investigations  and  publications  which 
have  brought  about  very  important  changes  in  that  branch 
of  chemical  science.  When,  therefore,  the  time  had  come  for 
issuing  a  new  edition,  the  Author  decided  not  to  go  over  the 
old  ground  again,  but  to  start  on  a  fresh  basis,  and  to  describe 
the  methods  of  Technical  Gas-Analysis  in  his  own  way,  using 
Winkler's  book  merely  as  one  of  various  sources,  apart  from 
his  own  investigations.  The  result  was  the  composition  of 
this  present  treatise,  which  the  Author  has  tried  to  make  as 
comprehensive  and  generally  useful  as  possible,  without 
attempting  to  mention  everything  published  on  the  subject 
in  question — a  course  which  would  have  unduly  swelled  the 
size  of  the  volume,  without  corresponding  benefit  to  the  reader. 
He  hopes  that  his  effort  may  be  appreciated  as  successful  by 
the  chemists  working  on  Gas-Analysis. 

G.   LUNGE. 
ZURICH,  July  1914. 


vii 


CONTENTS 


GENERAL   REMARKS   ON   TECHNICAL   GAS-ANALYSIS 


Difference  between  scientific  and  tech- 
nical gas-analysis,  with  respect  of 
the  degree  of  accuracy  required  .         I 
Necessity  of  obtaining  the  results  in 
a  short  time,  involving  the  use 
of  special  apparatus    ...         2 
Results   generally  to   be   stated  for 
"  normal ''  conditions  of  tempera- 
ture, pressure,  and  moisture         .         2 
Enumeration  of  the  processes  employed 

in  gas-analysis   ....         2 

Sampling  ......         3 

Necessity  of  taking  frequent  samples        3 
Choosing  the  proper  place     .         .         3 
Previous  removal  of  the  air  from 

the  apparatus  ...         4 

Aspirating  pipes — material    .         .         4 

Where  to  put  them    ...         5 

Pipes  for  sampling  hot  gases .         .         5 

Cooling  arrangement  for  metallic 

aspirating  tubes      ...         6 
Automatic  gas  sampler  ...         8 
Aspirating  apparatus      ...         8 
India-rubber  blowers      ...        9 
Steam-jet  aspirators       ...         9 
Sprengel  pumps  (Bunsen  pumps)  .       10 
Water-jet  pumps   .         .         .  II 

Aspirating  bottles.         .         .         .12 

Vessels  for  collecting,  keeping,  and 

carrying  samples  of  gases        .       14 
The  measurement  of  gases   .         .        .17 
Conditions  of  the  "normal"  state 
of  temperature,  pressure,  and 
moisture         .        .        .  17 

Formula  for  reducing  the  volume 

to  the  "  normal  "  state     .         .       18 


PAGE 

The  measurement  of  gases — continued. 
Apparatus  for  the  mechanical  re- 
duction   of    the    volumes    of 
gases  to  the  normal  state        .       19 

Tubes 20 

The  gas- volumeter  .  .  .21 
Application  to  gas-burettes  .  22 
Setting  of  the  reduction-tube  for 

moist  or  dry  gases       .         .       24 
Reduction-tubes  readily  filled  for 

sale 26 

Connection  of  the  three  tubes     .       26 
Manipulation   of    the   gas-volu- 
meter   27 

Application  for  estimation  of 
carbon  dioxide,  carbon, 
hydrogen  peroxide,  nitrogen, 


etc. 


Measuring  apparatus  for  gases     . 

Graduation 

Confining  liquid  (water  or  mercury) 
Influence  of  this  on  the  meniscus 

correction        .... 
Solubility  of  gases  in  water    . 
Contrivances  for  a  correct  reading 

of  the  level  of  the  liquid  . 

A  djustment  or  calibration  of  gas-measur- 
ing apparatus      .... 
Meniscus  corrections   for  mercury 
and  water        .... 
Calibration  of  apparatus  working 
with   liquids  adhering   to  the 
glass  (water)  .... 
Ostwald's  pipette  .... 
The  true  litre 


29 

30 
30 
30 

31 
31 

32 


33 


34 


34 
37 
38 


CONTENTS 


Adjustment  or  calibration  of  gas-measur- 
ing apparatus — continued. 
Tables  and  rules  for  adjusting  the 

values  read  off  to  the  true  litre       40 
Adjustment    of    apparatus    where 

mercury  is  the  confining  liquid       42 
Double    meniscus    correction     for 

mercury          .         .         .         •       43 
Weights  of  a  cubic  centimetre  of 

mercury  at  various  temperatures      45 
Examination  of  apparatus,  adjusted 

for  mercury,  by  means  of  water       46 
Gas  measuring  tubes  with  a  milli- 
metre scale      ....      47 
Rules  of  the  English,  Austrian,  and 

American  bureaus  of  standards       47 

Measuring  in  gas-meters      .         .         •       47 

Description  of  a  wet  gas-meter       .       48 

Experimental  gas-meters        .         .       49 

Automatically  stopped  meters         .       49 

Meters  with  arbitrarily  divided  dials       49 

Gauging  gas-meters       ...       50 

Apparatus  for  measuring  the  volume  of 

gases  while  passing  through  tubes  .       50 

Various  apparatus  for  gas-analysis       .       50 

General 50 

A.  Apparatus   for   absorbing    and 

measuring  in  the  same  tube  : — 

1.  Winkler's  gas-burette     .         .       52 

2.  Lunge's  modification   of  the 

Winkler  gas-burette    .         .       55 

3.  Honigmann's  gas-burette       .       58 

4.  The  Bunte  burette         .        .       58 

B.  Apparatus  provided  with  absorb- 

ing  parts  separated  from  the 
measuring-tube       ...       65 


Various  apparatus  for  gas-analysis — 
continued. 

General      .         ...         .  65 

Orsat's  apparatus        ...  66 
Lunge's  modification  of  the  Orsat 

apparatus    .         .         .  71 
Further     modifications    of    the 

Orsat  apparatus  ...  76 
Hempel's  apparatus    ...  82 
His  gas-burette       ...  82 
His  modified  Winkler's   gas- 
burette    ....  84 
Absorption-pipettes    ...  84 
Simple  absorption-pipettes      .  84 
Pipette  for  fuming  oil  of  vitriol  8  5 
Tubulated    pipette    for   solid 

reagents  .         .         .         .85 

Composite  absorption-pipette .  86 

General  arrangement ...  86 

Manipulation      ....  87 

Principal  applications          .         .  89 
Estimation  of  methane  by  Hem 

pel's  explosion-pipette          .  90 
By  heated  platinum  wire          .  92 
Drehschmidt's  capillary      .         .  92 
Various  modifications  of   Hem- 
pel's    apparatus    by    other 
chemists      ....  93 
Apparatus  of  Ferdinand  Fischer .  95 
Of  Drehschmidt      .         .         .100 
Of  Pfeiffer       .         .         .         .103 
Various  apparatus      .         .         .  no 
Apparatus  for  the  rapid  and  con- 
tinuous analysis  of  gases         .  in 


VARIOUS    METHODS   EMPLOYED    IN   TECHNICAL 
GAS-ANALYSIS 


I.  ESTIMATION  OF  SOLID  AND  LIQUID 
ADMIXTURES  IN  GASES. 

General  remarks        .         .         .         .112 
Various  methods  for  solid  admixtures 

(soot,  dust,  etc.)          .         .         .113 
For  liquid  admixtures     .         .         .     u$ 


II.  ESTIMATION  OF  GASES  BY 
ABSORPTION. 

A.  By  gas-volumetric  methods      .         .lib 
Absorbing  agents  .         .         .         .     Il6 
General  remarks — 
(a)  Absorbent  for  carbon  dioxide  .     117 


CONTENTS 


XI 


II.  ESTIMATION  OF  GASES  BY 

ABSORPTION— continued. 

A.  By  gas-volumetric  methods — contd. 

Solution  of  potassium  hydroxide     117 
(b~)  Absorbents   for   heavy   hydro- 
carbons :  (i)  fuming  sulphuric 

acid 117 

(2)  Bromine  water      .         .         .119 
(f)  Absorbents   for    oxygen  :    (i) 

phosphorus     .         .         .         .119 

(2)  Alkaline  solution    of    pyro- 
gallol 122 

(3)  Copper  ( immoniacal  cuprous 
oxide)          .         .         .         .124 

(4)  Sodium  hydrosulphite .         .     125 

(5)  Chromium  protochloride      .     125 

(6)  Alkaline  solution  of  ferrous 
tartrate        .         .         .         .125 

(//)  Absorbents    for   carbon   mon- 
oxide :     ammoniacal    solution 
of  cuprous  chloride          .         .     126 
Removal  of  last  traces        .         .127 
Colorimetrical  test      .         .         .128 
(i)    Absorbent  for  nitrogen    .         .128 
(/)  Absorbents  for  nitric  oxide       .     128 
(,§)  Absorbent  for  hydrogen   .         .129 
Palladium  sponge       .         .         .     129 
Palladiumsol      .         .         .         .130 
(/?)  Absorbents     for     unsaturated 

hydrocarbons.         .         .         .132 

B.  Estimation  of  gases  by   titration — 

General  remarks         .         .         .132 
Standard   solutions  indicating  the 

volume  of  the  gas  absorbed     .     133 
Measuring  either  the  total  volume 
or  the  non-absorbable  residue 

of  gas 133 

Apparatus  of  Hesse        .         .         .135 
Of  Reich,  modified  by  Lunge     .     137 
Application  for  the  estimation 
of    sulphur     dioxide     in 
pyrites-kiln  gases    .         .140 
Of  total  acids  in  the  same    .     141 
Of    sulphur     dioxide     and 

nitrous  gases        .         .141 
Of     the     sulphur     trioxide 
formed       in       contact 
apparatus     .         .         ,     142 
Minimetric    method    (Lunge    and 

Zeckendorf)    .         .         .         .142 


B.  Estimation  of  gases  by   titration — 

continued, 
Various     apparatus      for     minute 

quantities  of  gases  .  .  .  145 
Winkler's  absorption  coil  .  .  145 
Lunge's  ten-bulb  tube  .  .  146 
Volhard's  absorbing  flask  .  .  147 
Drehschmidt's absorbing  cylinder  147 

C.  Estimation  of  gases  by  weight          .     147 
Estimation  of  hydrogen  sulphide, 

carbon  disulphide,  and  acety- 
lene in  coal-gas       .         .         .     147 
Of  total  sulphur  in  coal-gas         .     149 
Of     sulphuretted     and      phos- 
phoretted  hydrogen  in  acety- 
lene      150 

Detection  and  approximate  estima- 
tion of  sulphur  dioxide  and 
sulphuric  acid  in  air,  suspected 
of  being  contaminated  by  acid- 
smoke  150 

III.  ESTIMATION  OF  GASES  BY 

COMBUSTION. 

General  observations          .         .         .     151 
Changes  of  volume  by  the  combustion 
and    calculation    of    the    single 
combustible     gases    (hydrogen, 
methane,  carbon  monoxide)  there- 
from ...         .         .         .     151 

Ethane  .         ...         .         .     155 

Methods  of  combustion — I.  Ordinary 

combustion         .         .         .         .155 

II.  Special  methods — 

1.  By  explosion          .         .         .155 
Hempel's  apparatus         .         .156 

His  hydrogen  pipettes         .  158 

Manipulation      .         .         .  160 
Estimation  of  hydrogen  in  the 

absence  of  methane  .         .  160 

Of  nitrogen         .         .        .  161 
Of  methane  in  the  absence 

of  hydrogen          .        .  161 
Of  hydrogen  and  methane 

occurring  together        .  162 

Analysis  of  coal-gas        .        .  162 

Pfeiffer's  explosion-pipette      .  1 63 

2.  Combustion     by     means     of 

heated  platinum  or  palladium 
(fractional  combustion)         .     416 


xii 


CONTENTS 


III.  ESTIMATION  OF  GASES  BY 

COMBUSTION— continued. 
Methods  of  combustion — continued. 

Winkler's  apparatus        .         .164 
Preparation      of      palladium 

asbestos  ....     165 
Manipulation .         .         .         .166 
Investigation   of   Richardt  on 
the  catalytic  action  of  hot 
palladium         .         .         .168 
Bunte's   process   of   fractional 

combustion  over  palladium    1 69 

3.  Combustion    of    methane   by 

heated  platinum  .         .         .172 

4.  Combustion    of    nitrogen   by 

oxygen  through  the  action 

of  electric  sparks          .         .172 

5.  Combustion  by  cupric  oxide  .     172 

IV.  GAS-ANALYSIS  BY  OPTICAL  AND 

ACOUSTICAL  METHODS. 
Haber's    Refractometer    and    Inter- 
ferometer    176 


V.  SEPARATION  OF  GASES  BY  Low 
TEMPERATURES 


178 


VI.  ESTIMATION  OF  SPECIFIC  GRAV- 
ITY OF  GASES. 
General 178 

(a)  Calculation     of    the     specific 
gravity  from  the  analysis         .     179 

(b)  Determination  of  the   specific 

gravity  of  a  gas  by  measuring 
its  velocity  when  issuing  from 
an  orifice  .  .  .  .  1 80 


PAGK 

VI.  ESTIMATION  OF  SPECIFIC 
GRAVITY  OF  GASES  -continued. 

General — continued. 

Apparatus  of  Schilling        .         .     181 

(c)  The  gas  balance  of  Lux  .        .183 

(d)  Other  apparatus  for  this  purpose     189 
Estimation  of  the  specific  gravity  of 

gases  in  motion  .        .        .         .187 


VII.  MEASUREMENT  OF  PRESSURE 
AND  OF  DRAUGHT. 

Pressure  gauges  (manometers) 


VIII.    DETERMINATION    OF    THE 
CALORIFIC  VALUE  OF  GASES. 

General 

Units  of  heat 

Gross  and  net  calorific  power     . 

Standard  temperature  and  pressure   . 

Calculation  of  the  calorific  value  of 
gaseous  mixtures  from  the 
analysis 

Table  of  the  calorific  power  of  sample 


The     direct     measurement     of    the 

calorific  power    .         .  » 

General 

(a)  Gas-calorimeter  of  Junckers     . 

0$)  Of  Boys 

(0  Of  F.  Fischer  .        .        . 

(d)  Various  gas-calorimeters  . 

IX.  DETERMINATION  OF  THE  ILLU- 
MINATING POWER  OF  GASES  . 


188 


190 
191 
192 

192 


193 
194 

196 
196 
197 

201 

207 
209 


210 


SPECIAL  METHODS  FOR  DETECTING  AND  ESTIMATING 
VARIOUS  GASES  AND  VAPOURS  OCCURRING  IN  TECHNI- 
CAL OPERATIONS 


Oxygen  apparatus  of  Lindemann         .     211 

Method  of  Pfeiffer          .        .        .211 

Of  Lubberger    .        .        .        .216 

Other  methods       .         .        .        .217 

Ozone 219 

Hydrogen  peroxide     .         .         .         .221 


Carbon     dioxide    apparatus     of     Cl. 

Winkler 222 

Of  Hesse 223 

Of  Pfeiffer 225 

OfRiidorff 227 

Other  apparatus     .         .         .         .229 


CONTENTS 


xiii 


Carbon  dioxide — continued. 
Apparatus  for  the  rapid  and  con- 
tinuous estimation  of   carbon 
dioxide  in  free  gases,  etc.         .     230 
Of  Arndt("Ados")  .         .         .231 
Othei  apparatus          .         .         .     233 
Strache's  "autolysator"      .         .     233 
Other  apparatus          .         .         •     235 
Various  methods  for  the  estimation 

ofC02 236 

Carbon  monoxide  .  .  •  .237 
Qualitative  detection  .  .  .  237 
Quantitative  determination  .  .239 

Sulphur  dioxide 243 

Apparatus  of  Ljungh     .         .         .     243 
Estimation  in  the  presence  of  nitrous 

vapours 244 

Estimation  of  total  acids(SO2  +  SO3): 

Apparatus  of  Lunge        .         .     245 
Of  the  English  Alkali  Inspectors     245 

OfHenz 246 

Estimation  by  the  specific  gravity 

of  kiln-gases   ....     246 
Estimation  of  sulphur  dioxide  and 

trioxide  alongside  of  each  other    247 
Sulphuretted  hydrogen         .         .         .     248 
Detection  in  street-gas  .         .        .     248 
Gravimetric  estimation  .         .         .     249 
Volumetric  estimation    .         .         .250 
Colorimetric  estimation .         .         .251 
Estimation  of  sulphur  dioxide  and 
sulphuretted  hydrogen  in  pre- 
sence of  each  other  .         .252 
Other  sulphur  compounds    .         .         .253 
Organic  compounds       .         .         .253 
Qualitative  detection .         .         .     253 
Carbon  disulphide,  qualitative  de- 
tection    .         .         .         .         .     254 
Quantitative  estimation       .         .255 
Carbon  oxysulphide       .         .         .     256 
Total  sulphur  in  coal-gas        .         .257 
Method  of  the  Metropolitan  Gas 

Referees      .        .         .         .257 

Similar  methods          .         .         .     259 

Method  of  F.  Fischer         .         .     260 

Of  Drehschmidt      .         .         .     260 

Other  methods  ....     264 

Hydrogen 265 

Detection 265 

Quantitative  estimation          .         .     266 


PACK 

Methane 266 

Grisoumeter  of  Coquillion      .         .     267 
OfWinkler        .        .        .         .269 

Of  others 271 

Winkler's   method    for  examining 
coal-pit    air    containing    very 
small  quantities  of  methane    .     272 
Method  of  Fresenius      .         .         .     275 
Of  Hempel        ....     276 
Of  Haber  (Schlagwetterpfeife)  .     277 
Mixtures  of  hydrogen  with  satur- 
ated    gaseous     hydrocarbons 
(methane,  ethane,  etc.)  .         .279 

Acetylene 281 

Qualitative  reactions  .  .  .  281 
Quantitative  estimation  .  .  282 
Impurities  contained  in  crude 

acetylene        .         .         .         .282 
Estimation  of  hydrogen   sulphide 

and  phosphide         .         .         .     282 

Ethylene 286 

Action  of  bromine  water  .  .  286 
Method  of  Haber  and  Oechelhauser  287 

Benzene 288 

General 288 

Volumetric  methods  .  .  .  289 
Estimation  by  absorption  with 

nickel  compounds  .        .        .289 

By  cold  paraffin  oil    .         .         .     289 

By  bromine  water       .         .         .     290 

By   converting    it  into   dinitro- 

benzene;  method  of  Harbeck 

and  Lunge  ....    290 

OfPfeiffer          .        .        .        .293 

By  freezing  out          ...     295 

Calculation  from  the  specific  gravity     296 

General  remark      .         .         .         .298 

Naphthalene  vapour    .         .         .         .298 

Method  of  Colman  and  Smith        .     299 

OfPfeiffer 300 

Of  Jorissen  and  Rutten      .        .     301 

Other  methods       .        .        .        .302 

Total  heavy  hydrocarbons  in  coal-gas    .     304 

Tar  vapours 3°5 

Importance  of  testing  for  them      .     3° 5 

Qualitative  tests    .         .         .         .306 

Quantitative  estimation          .         .     3°6 

Method  of  Tieftrunk      .        .        .306 

Of  Clayton  and  Skirrow     .         .     307 

OfFeld 308 


XIV 


CONTENTS 


Detection  of  inflammable  gases  or  vapours 

in  the  air 309 

Apparatus  of  Philip  and  Steele      .     309 
Of  Guasco          .         .         .         .313 

Ferrocarbonyl 313 

Nitroglycerine 314 

Nitrogen  protoxide  (Nitrous  oxide)       .     314 

Nitric  oxide 316 

Estimation  by  absorption  .  .31? 
By  oxidation  to  nitric  acid  .  .  317 
By  combustion  in  the  presence  of 

caustic  potash          .         .         .318 
By  combustion  with  hydrogen  or 

carbon  monoxide    .        .         .319 
Nitrogen  protoxide  and  nitric  oxide 

in  the  same  gas  mixture .         .     320 
Estimation  of  nitrogen  protoxide, 
nitric  oxide,  and  nitrogen  in 
the  same  mixture    .         .        .321 
Nitrogen  trioxide  and  peroxide     .         .322 

Free  nitrogen 324 

Ammonia  ,         .         .         .         .  325 

Pyridine 327 

Cyanogen  and  hydrogen  cyanide  .         .328 
Hydrogen  chloride     .         .         .         .333 
Exit-gases  from  the  condensers  in 
the  manufacture  of  sulphate  of 
soda  from  common  salt  in  de- 
composing pans      .        .        .     333 
Gases  evolved  in  the  Hargreaves 

process 335 

Examination  of  gases  in  the  manufacture 
of  sulphuric    acid    by    the    lead- 
chamber  process  .         .         .         .336 
(i)  Gases  before  entering  into  the 

chambers        ....     336 


Examination  of  gases  in  the  manufacture 
of  sulphuric  acid  by  the  lead- 
chamber  process — continued. 

(2)  Gases  of  the  lead  chambers     .       336 

(3)  Exit-gases  from  the  Guy-Lussac 

towers  (V)  free  oxygen   .         .     337 

(3)  Acids 339 

Total  acidity  ....     339 
Nitrogen  acids        .         .         .     340 
(c")  Nitric  oxide          .         .         .341 
(a?)  Nitrogen  protoxide       .         .     341 
(V)  Loss  of  sulphur  in  the  exit- 
gases  .         .         .         .         .342 
Chlorine    .         .  .         .         .     342 

Gases  of  the  Deacon  process  .  .  342 
Very  slight  quantities  of  chlorine 

in  the  atmosphere   .         .         .     344 
Estimation   of    carbon   dioxide  in 

electrolytic  chlorine  gas  .         .     348 
Detection   and   estimation   of  free 

chlorine  and  bromine      .         .351 
Impurities  occurring  in  atmospheric  air     351 
Phosphorus  trichloride  .         .         .352 
Fluohydric     and     hydrofluosilicic 

acid 352 

Hydrogen  phosphide  .  .  .  352 
Hydrogen  arsenide  .  ...  352 
Mercury  vapour  .  .  .  .  353 
Ether  vapour  .  .  ».  .  354 
Mercaptan  .  .  .  .  •  354 
Aniline  vapour  .  .  .  .354 
Tobacco  smoke  .  .  .  -354 
Injurious  effects  of  the  impurities 

of  air 355 


ANALYSIS   OF   GASEOUS   MIXTURES    PRODUCED   ON 
A   LARGE   SCALE 


Fire-gases     (smoke-gases,     furnace- 


356 


Producer-gases       (incl.      water-gas, 

Dowson  gas,  etc.)       .         .         .     356 
Coal-gas  (illuminating- gas)      .         .356 


COMPRESSED   AND    LIQUEFIED   GASES 


General  rules 357 

Table  of  properties  and  conditions  of 

carriage 358 

Sampling 358 

Measuring 360 


Apparatus  for  examining  the  gaseous 
impurities,  not  absorbed  by  the 
proper  absorbing  liquids  foi  the 
gas  under  examination  .  .  360 


CONTENTS 


xv 


Analysis  of  the  various  descriptions 
of  compressed  gases — 

(1)  Liquefied  sulphur  dioxide         .     361 

(2)  Liquefied  ammonia          .         .     362 

(3)  Liquefied  chlorine  .         .         .     365 


Analysis  of  compressed  gases — contd. 

(4)  Liquefied  carbon  dioxide          .  365 

(5)  Liquefied  nitrogen  protoxide   .  367 

(6)  Compressed  hydrogen     .         .  367 

(7)  Compressed  oxygen         .         .  368 


The  azotometer          . 
The  nitrometer  of  Lunge  . 

Other  forms 

Combination    with   decomposition 
bottle      .         .         .         .    .    . 

Reduction   of  the  gas  volume  to 
the  normal  state 


GAS-VOLUMETRIC   ANALYSIS 

The  nitrometer  of  Lunge— continued. 
Applications 


368 
372 
379 


38; 


Special  forms         .... 

Arrangement  and  fittings  of  a  labora- 
tory for  gas-analysis     . 


384 
385 

385 


APPENDIX 

I.  Atomic  Weights  fixed  by  the  International  Committee  for  1914         .         .         .  387 

II.  Theoretical  and  calculated  Density  of  Gases  and  Litre  Weights        .         .         .  388 

III.  Changes  of  Volume  when  Gases  are  burned  in  Oxygen     .....  389 

IV.  Combustion  of  Gases  and  Gaseous  Mixtures     .......  390 

V.  Standard  Solutions  for  Technical  Gas-Analysis 391 

ADDENDA 

Gas-sampling  apparatus 393 

Vessels  for  carrying  gas  samples 393 

Gas-an..lytical  apparatus 393 

Registering  gas  balance .        .         .         .         .  393 

Estimation  of  Carbon  monoxide 394 

ALPHABETICAL  INDEX  OF  NAMES 395 

ALPHABETICAL  INDEX  OF  SUBJECTS     .        . 402 


TECHNICAL    GAS- ANALYSIS 


GENERAL  REMARKS  ON  TECHNICAL 
GAS-ANALYSIS. 

THE  scope  of  technical  gas-analysis  naturally  differs  from 
that  of  gas-analysis  for  scientific  purposes,  as  we  need  not 
explain  in  detail.  We  will  only  point  out  that  technical  gas- 
analysis  is  principally  carried  out  in  two  directions :  firstly,  for 
the  checking  and  regulation  of  many  industrial  operations,  by 
which  solid,  liquid,  or  gaseous  products  are  obtained  ;  secondly, 
for  the  examination  of  gases  prepared  on  a  large  scale  as  final 
products  for  various  purposes. 

Especially  in  the  first  case  there  is  mostly  no  necessity 
of  attaining  the  same  degree  of  accuracy  as  is  justly  demanded 
for  scientific  purposes.  Even  if  such  accuracy  could  be 
attained,  it  would  not,  for  the  practical  purpose  in  question, 
(that  is,  for  the  checking  of  industrial  operations),  in  most  cases 
possess  any  greater  value  than  merely  approximate  estimations 
which  can  be  made  by  the  expenditure  of  much  less  time, 
with  simpler  apparatus  and  by  less  skilled  persons.  On  the 
contrary,  it  is  usually  infinitely  more  important  to  carry  out 
the  analytical  processes  in  as  short  a  time  as  possible,  in  order 
to  employ  the  result  for  regulating  the  technical  operation 
accordingly.  Even  if  a  whole  host  of  highly  trained  scientific 
chemists  were  at  disposal  (which,  of  course,  is  practically 
impossible),  their  results  would  come  in  too  late  and  be  useless 
to  the  technical  manager,  who  mostly  learns  all  he  requires 
for  his  purposes  by  rapid  and  frequent  tests,  often  carried  out 
by  merely  empirically  trained  persons. 

There  are  certainly  cases  where  even  for  the  manufacture 
of  commercial  products  the  greatest  obtainable  degree  of 
accuracy  in  testing  for  impurities  is  required,  and  here  all  the 
1  A 


s  TECHNICAL  GAS-ANALYSIS 

best  methods  known  must  be  employed.  Frequently  special 
methods  have  been  developed,  in  which  the  fullest  accuracy 
is  combined  with  the  possibility  of  reaching  this  in  a  short 
time.  These  exceptional  cases  will  be  dealt  with,  of  course, 
in  this  treatise.  Apart  from  these  we  claim  for  the  methods 
of  technical  gas-analysis,  as  for  technical  analysis  generally, 
that  they  should  be  carried  out  in  the  least  possible  time,  at 
that  degree  of  accuracy  which  is  required  for  their  specific 
purpose.  Just  on  this  account  frequently  special  apparatus 
are  employed  in  technical  laboratories,  which  we  do  not  find 
in  scientific  laboratories  where  time  is  no  object. 

Whether  the  analysis  of  gases  be  effected  for  scientific  or 
for  technical  purposes,  it  is  only  exceptionally  performed  by 
gravimetrical  methods,  but  mostly  volumetrically,  and  the 
results  are  consequently  in  most  cases  not  stated  in  per  cent, 
by  weight,  but  by  volume.  In  those  cases  where  gravimetrical 
methods  are  employed  in  this  field,  the  weights  found  are 
reduced  to  volumes,  for  which  purpose  a  number  of  tables  will 
be  found  in  this  treatise.  The  volume  of  the  gases  is  always 
calculated  for  "  normal "  conditions  of  temperature,  atmospheric 
pressure  and  moisture,  viz.,  for  a  temperature  of  o°,  a  pressure 
of  760  mm.,  and  the  perfectly  dry  state.  In  "technical"  gas- 
analysis  this  correction  may  be  sometimes  omitted  in  such 
cases  where  the  analyses  do  not  require  any  considerable 
degree  of  accuracy,  and  where  the  saving  of  time  is  an  object. 
For  the  purpose  of  carrying  out  technical  processes,  very 
accurate  results,  which  can  be  obtained  only  in  the  course  of 
many  hours  or  even  of  several  days,  as  is  sometimes  the  case, 
are  useless  for  the  management  of  the  works,  and  the 
employment  of  such  methods  must  be  restricted  to  scientific 
investigations. 

Burrell  and  Seibert  (%th  Intern.  Cong.  Appl.  Chem.  Appendix, 
xxv.  p.  189)  contend  that  the  ordinary  way  of  calculating  the 
results  of  gas-analysis  is  not  correct,  since  it  rests  on  the 
assumption  that  the  molecular  volumes  of  all  gases  are  alike, 
which,  according  to  them,  is  not  the  case.  However  that 
may  be,  technical  gas-analysis  will  not  be  affected  by  it. 

The  analytical  processes  employed  in  gas-analysis  belong 
principally  to  the  following  classes  : — 

ist.   Absorption    of  the    constituent    sought    for   from    the 


SAMPLING  3 

gaseous  mixture  by  a  liquid  or  solid  reagent,  and  measuring 
the  reduction  of  volume  thereby  effected. 

2nd.  Combustion  of  one  or  more  of  the  constituents,  after 
addition  of  oxygen  or  of  an  oxygen-producing  substance,  and 
measuring  the  contraction  thereby  effected,  sometimes  after 
removing  one  or  more  of  the  products  of  combustion  by 
absorbing  reagents. 

3rd.  Titration  of  the  constituent  sought  for  in  the  manner 
so  frequently  employed  in  both  scientific  and  technical  analysis. 

4th.  Gravirnetrical  estimations  of  a  gaseous  constituent  by 
absorbing  it  in  a  substance  with  which  it  forms  a  compound 
capable  of  being  weighed. 

SAMPLING. 

For  all  practical  purposes  it  is  just  as  important  that  the 
samples  of  the  gas  to  be  analysed  should  be  taken  in  the  proper 
manner,  as  that  the  analysis  itself  should  be  carried  out  correctly. 

In  very  many  cases  the  composition  of  the  gases  to  be 
analysed  varies  very  much  during  the  manufacturing  process. 
To  give  a  special  instance  : — 

Fire-gases  (chimney-gases)  from  steam  boilers  showed  in 
a  practical  case  : — 

1  minute  after  putting  12  minutes 

on  fresh  coal.  later. 

Carbon  dioxide       .  .       13-5  per  cent.  4-0  per  cent. 

Carbon  monoxide  .  .        o-o        „  oo        „ 

Oxygen       .  .  5-5         „  16-5 

Nitrogen    .  .  81-0        „  79-5         „ 

Smoky  particles     .  ...  present  absent 

In  all  such  cases  the  analysis  of  a  single  sample  rarely 
possesses  any  value.  But  even  the  continuous  drawing  off  a 
sample  of  the  gases  (for  which  purpose  Huntly,  in/.  Soc.  Chem. 
Ind.,  1910,  p.  512,  and  Gray,  ibid.,  1913,  p.  1092,  describe 
suitable  apparatus,  v.  infra)  rarely  represents  a  real  average  of 
their  composition.  A  truly  reliable  judgment  on  the  process 
going  on  in  the  fireplace  can  be  only  obtained  by  a  number 
of  single  tests,  taken  rapidly  after  one  another,  by  which  the 
influence  of  the  stoking,  etc.,  can  be  ascertained. 

Of  great  importance  is  also  the  place  at  which  the  sample  is 
taken.  Thus,  for  instance,  it  is  not  advisable  to  test  fire-gases 
by  samples  taken  out  of  the  chimney,  where  they  are  too  much 


4  TECHNICAL  GAS-ANALYSIS 

liable  to  be  diluted  by  air  drawn  in ;  the  sample  should  be 
taken  out  of  the  flue  leading  the  gases  to  the  chimney,  as  near 
as  possible  to  the  furnace. 

In  the  case  of  gas-conduits  of  somewhat  considerable 
dimensions,  the  composition  of  a  gaseous  mixture  frequently 
varies  at  different  places.  The  sample  tube  inserted  in  the  gas 
main  should  therefore  extend  through  the  pipe  or  channel  from 
side  to  side,  and  should  have  a  fine' longitudinal  exit,  or  a  series 
of  small  holes  all  along,  so  as  to  guarantee  as  much  as  possible 
the  average  composition  of  the  gas. 

Winkler  recommends  aspirating  a  strong  current  of  gas,  and 
employing  for  analysis  a  small  side-current,  by  means  of  a 
T-pipe. 

Before  collecting  the  gas,  the  air  must  be  completely 
removed  from  the  connecting  tubes  and  other  intermediary 
apparatus,  which  is  best  done  by  interposing  in  the  connecting 
tube  immediately  before  its  junction  with  the  collecting  vessel, 
a  ~[~-snaPed  branch  provided  with  a  tap.  If  the  gas  is  under 
pressure,  it  is  allowed  to  issue  from  that  side-branch  for  some 
little  time  before  closing  the  tap ;  if  there  is  no  pressure,  the 
side-branch  is  connected  with  a  small  india-rubber  aspirating 
pump,  by  means  of  which  the  air  is  removed  between  the  place 
whence  the  sample  is  taken  and  the  tubing  filled  with  the  gas 
to  be  analysed. 

The  aspirating  pipes  must,  at  the  temperature  to  which  they 
are  exposed,  be  capable  of  resisting  both  the  heat  and  the 
chemical  action  of  the  gases. 

India-rubber  tubes  must  therefore  not  be  employed,  except 
in  short  pieces  for  connecting  tubes  of  other  material,  the  ends 
of  which  are  brought  closely  together.  Even  thick-walled 
rubber  tubes  allow  the  passage  of  small  quantities  of  gas,  but 
they  are  very  much  improved  by  painting  with  copal  varnish 
(Lunge  and  Harbeck,  Z.  anorg.  Ckern.,  xvi.  p.  30). 

Wherever  possible,  glass  tubes  are  employed,  which  are 
chemically  indifferent  and  easy  to  clean. 

For  taking  samples  out  of  spaces  where  glass  would  soften 
or  fuse,  porcelain  tubes  are  usually  employed  of  such  length 
that  the  gases  are  sufficiently  cooled  down  before  they  are 
conveyed  further  on  in  glass  tubes.  Porcelain  tubes  are  liable 
to  crack  if  they  are  suddenly  exposed  to  high  temperatures, 


SAMPLING  5 

and  they  must  therefore  be  carefully  heated  up  before  putting 
them  in.  Quartz  tubes  are  not  exposed  to  cracking,  but  they 
can  be  employed  only  up  to  1000° ;  above  this  they  are  not 
gas-tight.  Unglazed  earthenware  tubes  are  of  course  much 
too  porous  for  this  purpose. 

The  aspirating  tubes  are  put  in  a  suitable  hole  in  the 
place  from  which  the  samples  are  to  be  taken.  In  many  cases 
they  may  be  fixed  there  by  means  of  a  cork,  or  an  india-rubber 
stopper,  e.g.  in  the  side  of  a  vitriol-chamber,  or  in  other  places 
where  the  temperature  admits  of  it.  Where  it  is  possible,  a 
special  short  side-tube  is  put  in  the  apparatus  for  that  purpose. 


FIG.  i. 


In  other  cases,  especially  where  masonry  has  to  be  penetrated 
(e.g.  in  gas-producers  or  fire-flues),  a  short  earthenware  or 
porcelain  pipe  is  inserted,  and  the  aspirating  tube  fixed  in  it  by 
some  cement,  fire-clay,  etc. 

The  porcelain  or  quartz  tubes  used  for  aspirating  hot  gases 
should  be  of  such  a  length  as  to  project  a  good  deal  on  the  out- 
side. This  projecting  part  may  be  filled  with  asbestos  or  glass- 
wool,  in  order  to  retain  soot,  ashes,  etc.,  as  shown  in  Fig.  I. 

For  taking  gas  samples  from  Bessemer  converters,  F.  Fischer 
(Z.  Verein.  deutsch.  Ingen.,  1902,  pp.  1006  and  1367)  employs  the 
aspirating  arrangement  shown  in  Fig.  2.  A  porcelain  tube  c 


6 


TECHNICAL  GAS-ANALYSIS 


is  placed  inside  an  iron  tube  b,  the  two  being  held  together  at 
a  by  a  collar  of  fireclay ;  the  porcelain  tube  projects  about  5 
cm.  beyond  the  iron  tube.  This  apparatus  is  placed 
horizontally  across  the  top  of  the  converter,  in  such 
manner  that  the  end  of  the  porcelain  tube  is  just 
over  the  gas  current.  A  glass  tube  s  is  joined  to 
the  porcelain  tube  by  a  cement  of  clay  and  of  sodium 
silicate  solution,  and  at  its  other  end  is  connected 
by  india-rubber  tubing  gt  with  a  number  of  glass 
bulbs,  «,  n}  with  capillary  entrance-  and  exit-tubes. 
By  means  of  an  aspirator  (which  may  be  a  water- 
vessel  of  the  usual  shape,  or  an  india-rubber  pump) 
the  gases  are  aspirated  out  of  the  converter  into  the 
glass  bulbs,  and  once  every  two  minutes  a  bulb  is 
removed  after  sealing  off  the  capillary  ends.  In 
order  to  perform  this  operation  in  the  open  air, 
Fischer  employs  the  small  oil-lamp  shown  in  Fig.  3, 
in  half  its  real  size,  d  is  the  wick-holder ;  B  a  tin- 
cap,  with  air-holes,  c,  c,  at  its  lower  end,  a  larger 
orifice  at  the  top,  and  a  circular  side-hole  e,  from 
which  issues  the  flame  blown  out  by  the  point  n  of 
a  blowpipe. 

Frequently  metallic  aspirating  tubes  (made  of 
iron,  brass,  copper,  silver,  platinum)  are  employed. 
They  are,  of  course,  not  liable  to  breaking,  but  can 
only  be  employed  where  the  temperature  does  not 

reach  the  softening  or 
fusing  point  of  the 
metal  in  question,  and 
where  no  chemical 
action  of  the  gas  on 
the  metal  can  take 
0|rf![Q  0C0  place.  Owing  to  their 
great  conductivity  for 
heat,  which  might  de- 
stroy the  corks  or  india- 
FIG.  2.  FIG.  3.  rubber  in  contact  with 

the  metal,  they  must  in 

many  cases  be  provided  with  a  cooling  arrangement.     For  this 
purpose  Winkler  recommends  an  arrangement  shown  in  Fig.  4. 


n 


ASPIRATING-TUBES 


7 


Three  concentric  copper  tubes,  of  i  or  2  mm.  metal  thick- 
ness, are  connected  in  the  way  shown  in  the  figure.  The  inner- 
most tube  a  is  5  mm.  wide;  this  is  the  aspirating  tube. 
It  is  surrounded  by  tube  b,  12  mm.  wide,  which  is  soldered  up 
tight  at  one  end,  the  other  end  towards  A  being  left  open. 
The  side  branch,  d,  with  a  stopcock,  admits  the  cooling-water. 


FIG.  4. 

This  tube  is  again  surrounded  by  tube  c,  20  mm.  wide,  which 
at  the  end  A  is  soldered  to  tube  a,  and  at  the  other  end 
(near  B)  to  tube  b.  Tube  c  is  also  provided  with  a  branch  c, 
through  which  the  cooling-water,  introduced  by  </,  which  has  got 
heated  on  its  way  through  tubes  b  and  c,  runs  out.  The  length 
of  tube  AB  may  vary  according  to  circumstances ;  usually 
about  2  feet  will  suffice. 

This   apparatus   is    placed    in   the   furnace   wall,   in   which 


FIG.  5. 

a  suitable  hole  has  been  made.  The  stopcock  d  is  connected 
by  an  india-rubber  pipe  with  a  water  pipe ;  it  is  then  opened, 
and  as  soon  as  the  water  issues  at  e,  the  end  A  is  introduced 
into  the  furnace,  and  the  joint  is  made  good  by  a  wet  mixture 
of  fireclay  and  common  clay.  End  a  is  now  connected  with  an 
aspirator  and  with  the  reservoir  for  the  gas  to  be  sampled. 

Drehschmidt   (Post's    Chem.    Techn.  Anal,   3rd   ed.  p.   no) 
employs    the    simpler   arrangement    shown    in    Fig.    5.     The 


8  TECHNICAL  GAS-ANALYSIS 

aspirating  tube  a,  4  or  5  mm.  wide,  is  surrounded  by  a  jacket 
b,  closed  at  both  ends,  into  which  cold  water  is  introduced  by 
pipe  ay  and  runs  out  continuously  at  d.  The  pipes  are  made  of 
copper  and  the  joints  are  brazed. 

Tread  well  (Quant.  Anal.,  5th  ed.  p.  600)  recommends  a 
similar  arrangement,  the  St  Claire  Deville  cold-hot  tube, 
made  of  iron,  as  shown  in  Fig.  6.  A  rapid  stream  of  cooling- 
water  enters  at  a  and  issues  at  b\  the  gas  is  taken  out  by  the 
tap  c.  These  tubes  admit  of  taking  gas  samples  from  various 
heights  of  the  red-hot  coal  in  gas-producers  and  blast-furnaces. 
Care  must  be  taken  to  run  the  water  through  with  such  rapidity 
that  it  comes  out  cold  at  b. 

In  the  same  place  Treadwell  shows  an  apparatus  for  taking 
gas  samples  from  inaccessible  places,  and  another  for  collecting 
the  gases  given  up  freely  from  mineral  springs, 
or  absorbed  in  spring  water. 

Fischer  (Dingl.  J.}   ccxxxii.    p.    528)  points 
out   that,  where  iron   tubes   are  employed  for 
aspirating  the  gases,  the  rust  forming  thereon 
may  greatly  alter  the  composition  of  the  gases. 
In  very  hot  gases  the  constituents  may  be 
in   a   state  of  dissociation,   and   if  during   the 
aspiration     they    are    rapidly    cooled,    carbon 
monoxide  may  be  found  co-existing  with  free 
oxygen,  whereas  in  gradual  cooling  these  two  would  combine 
to  form  CO2. 

Winkler  (Winkler-Lunge,1  p.  10)  describes  an  apparatus  for 
cooling  the  gases  by  immediate  contact  with  water,  but  this 
process  can  be  employed  only  where  the  gases  soluble  in 
water  can  be  neglected,  and  it  is  therefore  applicable  only  in 
exceptional  cases. 

Gray's  automatic  aspirating  apparatus  is  described  on  p.  n. 

ASPIRATING  APPARATUS. 

Wherever  the  gas  to  be  sampled  is  under  a  higher  than  the 
atmospheric  pressure,  as  a  rule  no  special  apparatus  is  needed 
for  taking  the  samples.  In  the  contrary  case,  where  the  gas 

1  By  this  designation  ("  Winkler-Lunge ")  we  quote  Winkler's  Hand- 
book of  Technical  Gas- Analysis,  translated  by  Lunge,  second  English 
edition,  London,  1902. 


ASPIRATORS  9 

does  not  of  its  own  accord  enter  into  the  absorbing  tubes  or 
other  analytical  apparatus,  special  aspirators  must  be  employed 
which  may  be  "  dry  "  or  "  wet "  aspirators. 

As  dry  aspirators,  in  many  cases  india-rubber  hand  or  foot 
blowers,  of  the  usual  commercial  description,  may  be  used  for 
taking  the  samples.  Such  blowers  are  shown  in  Fig.  7.  The 
india-rubber  vessel  A  is  closed  at  both  ends  by  wooden  bungs 


FIG.  7. 

or  corks,  containing  inside  a  simple  kind  of  leather  clock-valve. 
Through  one  of  these  passes  the  aspirating  tube  a,  through  the 
other  the  discharging  tube  b.  On  compressing  the  vessel  A  by 
hand  or  foot,  its  gaseous  contents  are  forced  out  through  b ; 
where  the  pressure  is  relaxed,  A  resumes  its  former  shape,  and 
thereby  aspirates  gas  through  a.  By  repeating  this  manipula- 
tion, considerable  quantities  of  gas  may  be  aspirated  within 


FIG.  8. 

a  short  time.  No  confining  liquid  comes  into  question  in  this 
case,  but  this  contrivance  can  only  be  used  where  there  is  an 
ample  supply  of  the  gas  to  be  examined,  for  the  air  previously 
present  in  the  blower  must  be  completely  driven  out  and 
replaced  by  an  excess  of  the  gas  to  be  analysed. 

Fig.  8  shows  a  steam-jet  aspirator.  A  strong  glass  tube, 
or  in  cases  where  the  gas  does  not  act  upon  metal,  a  metallic 
tube,  3  cm.  wide  and  20  to  25  cm.  long,  has  a  tapering  end, 


10 


TECHNICAL  GAS-ANALYSIS 


with  a  6-mm.  orifice.  A  steam-pipe  passes  through  it,  the 
end  of  which,  tapering  down  to  2-mm.  bore,  ends  about  12 
mm.  behind  the  orifice  of  the  outer  tube.  Near  this  point 
the  steam-pipe  is  held  in  its  place  by  a  wooden  or  metallic 
ferrule,  a;  at  the  other  end  it  is  tightly  fixed  in  the  cork  by 

which  also  holds  the  tube  e  for  the  gas 
to  be  aspirated;  c  is  a  layer  of  cement; 
d  a  metallic  ferrule  ;  f  an  india-rubber 
pipe  with  hemp  lining,  making  con- 
nection with  the  steam-pipe  g. 

Of  "  wet "  aspirators  many  descrip- 
tions have  been  constructed,  only  a 
few  of  which  are  to  be  mentioned 
here. 

One  of  the  most  widely  used  wet 
aspirators  is  Sprengel's  water-air  pump 
(frequently  but  erroneously  designated 
as  "  Bunsen  pump ")  shown  in  Fig.  9. 
A  cylindrical  glass  vessel  A  is  at  its 
contracted  upper  end  connected  by 
soldering  with  the  glass  tube  c,  the 
top  of  which  is  bent  downwards  and 
communicates  with  the  glass  vessel  B. 
c  descends  inside  A  nearly  down  to  its 
lower  contraction,  where  it  ends  in  a 
fine  orifice.  The  bottom  end  of  A  is 
narrowed  and  connected  with  a  lead 
pipe  £,  8  mm.  wide,  10  to  12  metres 
long,  and  bent  up  at  the  lower  end 
so  that  some  water  is  retained  there. 
The  vessel  A  also  possesses  a  side- 
branch  a,  continued  into  an  india- 
rubber  pipe,  connected  with  a  water- 
reservoir  or  service-pipe.  The  flow  of 
water  can  be  once  for  all  set  to  a  certain  rate  by  means  of 
a  screw  clamp,  and  completely  shut  off  by  another  clamp. 
When  the  running  of  water  through  a  is  started,  pipe  b  is 
filled  with  a  column  of  water  balancing  the  weight  of  the 
atmosphere,  and  the  water  following  this  aspirates  air  (or 
gas)  through  c,  which  is  yielded  up  at  the  lower  end  of  b. 


FIG.  9. 


ASPIRATORS 


11 


As  long  as  c  remains  open,  the  air  is  continuously  sucked  in, 
while  the  flow  of  water  is  going  on.  If,  however,  c,  or  a  space 
communicating  with  c,  is  closed,  a  vacuum  is  produced  by 
the  action  of  the  water-barometer  formed  by  the  apparatus. 
Vessel  B  is  not  essential  for  the  purpose  of  aspiration,  but 
it  serves  for  retaining  any  liquid  carried  on  mechanically, 
which  is  from  time  to  time  discharged  through  /  Tube  d  is 
connected  with  a  mercurial  pressure  gauge,  which  indicates 
the  progress  of  the  evacuation.  Tube  e  is  connected  with  the 
space  to  be  evacuated,  or 
from  which  a  sample  of 
gas  is  to  be  taken. 

If  the  Sprengel  pump 
is  not  to  serve  for  com- 
pletely evacuating  the  air 
from  a  given  space,  but 
only  for  aspirating  gases, 
tube  b  need  not  be  more 
than  say,  I  metre  long. 
In  lieu  of  a  lead  tube,  it 
may  then  be  an  india- 
rubber  tube,  closed  at  its 
lower  end  by  a  bent  glass 
tube. 

An  improved  form  of 
mercurial  gas-pumps  is 
that  constructed  by  Topler 
which  is  sold  by  all  dealers 
in  chemical  apparatus. 

A  number  of  water- 
jet  pumps  have  been  con- 
structed by  various  inventors,  e.g.  Arzberger  and  Zulkowsky, 
H.  Fischer,  Korting  Brothers,  Ph.  Schorer.  They  require  no 
special  height  of  fall  for  the  waste  water,  but  a  head  of  5  to 
10  metres  water  for  feeding.  As  an  example  of  the  way  in 
which  they  work  we  refer  to  Fig.  10.  The  water  enters  at  A, 
issues  from  the  conical  tube  a,  i  mm.  bore,  carries  along  the 
air  entering  through  B,  passes  the  contracted  part  b,  and  runs 
off  at  C.  The  three  tube-ends,  A,  B,  and  C,  are  connected 
by  elastic  tubing  with  the  corresponding  pipes. 


FIG.  10. 


12 


TECHNICAL  GAS-ANALYSIS 


Hardly  less  efficient  are  the  various  water-jet  pumps  made 
of  glass,  which  can  be  connected  with  any  water-tap  by  means 
of  thick  india-rubber  tubing.  We  show  here  in  Fig.  n 
Finkener's  aspirator,  where  the  water  enters  from  the  service- 
pipe  through  the  tube  a,  drawn  out  to  a  point;  it  runs  away 
through  tube  e,  which  is  widened  at  the  top  and  bottom ;  the 
air  aspirates  through  b  and  forms  a  frothy  mixture  with  the 
water  issuing  at  c.  This  tube  is  made  in  two  pieces,  connected 


e  c 

FIG.  ii.  FIG.  12. 

by  an  india-rubber  tube  in  order  to  diminish  its  fragility. 
Geissler's  water-jet  aspirator,  shown  in  Fig.  12,  can  be  under- 
stood without  special  explanation. 

In  many  cases  the  gas-burette  or  the  gas-collecting  bottle 
themselves  are  employed  as  aspirators,  by  being  filled  with 
water,  which  is  either  run  off  within  the  space  containing  the 
gas  to  be  examined,  or  after  connecting  the  apparatus  with  the 
aspirating  tube. 

For  collecting  somewhat  large  quantities  of  gas,  aspirating 


ASPIRATORS 


13 


bottles  may  be  employed  as  shown  in  Fig.  1 3.  The  bottle  A  is 
placed  on  a  wooden  stool ;  its  india-rubber  stopper  is  provided 
with  a  glass  stopcock  a  and  a  tube  b,  reaching  nearly  down  to 
the  bottom  of  A,  and  connected  by  elastic  tubing  with  a  straight 
glass  pipe  acting  as  a  syphon.  The  elastic  tube  can  be  closed 
entirely  or  partially  by  a  screw  clamp.  Before  taking  the 
sample,  bottle  A  is  filled  with  water  through  tube  b  in  such 


a 


FIG.  13. 

manner  that  no  air-bubbles  remain  and  that  the  water  rises 
up  to  the  stopcock  a.  Now  all  the  air  is  removed  from  pipe  a 
by  means  of  the  pump  c ;  and  the  gas  is  aspirated  by  allowing 
the  water  to  flow  out  into  B.  Such  an  arrangement  can,  for 
instance,  serve  for  continously  taking  a  sample  from  the  main 
current  of  gases  developed  during  a  length  of  time. 


H  TECHNICAL  GAS-ANALYSIS 

Aspirators  of  the  same  class,  but  made  in  a  more  substantial 
manner,  are  sold  by  most  dealers  in  chemical  instruments.1 

An  automatic  gas-sampling  apparatus ',  which  permits  of 
regularly  taking  samples  from  a  current  of  gas,  and  thus  to 
obtain  an  average  sample,  is  described  by  Thomas  Gray  in 
/.  Soc.  Chem.  Ind.,  1913,  p.  1092.  From  a  collecting  vessel 
filled  with  mercury,  water,  or  an  aqueous  solution  of  glycerin  or 
magnesium  chloride,  the  confining  liquid  is  constantly  running 
out,  and  thus  gas  is  constantly  aspirated  into  the  vessel.  The 
ordinary  industrial  gaseous  fuels  and  the  products  of  their 
combustion  may  be  stored  over  concentrated  aqueous  solutions 
of  glycerin  or  magnesium  chloride  for  short  periods  without 
considerable  change  of  composition,  but  prolonged  contact  and 
agitation  with  the  confining  liquid  should  be  avoided. 

VESSELS  FOR  COLLECTING,  KEEPING,  AND 
CARRYING  SAMPLES  OF  GASES. 

Unless  it  is  unavoidable,  samples  of  gases  taken  for  analysis 
should  not  be  kept  for  any  length  of  time,  but  ought  to  be 
transferred  at  once  to  the  gas-burette  or  absorption  bottle, 
in  order  to  be  instantly  analysed.  Where  it  cannot  be  avoided 
to  employ  water-luting,  the  water  must  be  brought  merely 
into  superficial  and  momentary  contact  with  the  gas,  and  the 
gas  should  not  pass  through  the  water  itself y  as  it  must  do  in  a 
pneumatic  trough.  Otherwise  the  solvent  action  of  the  water, 
which  is  entirely  different  towards  different  gaseous  substances, 
would  essentially  alter  the  composition  to  the  gas. 

If  the  collection  of  the  gas  in  a  separate  vessel  for  the 
purpose  of  keeping  it  for  some  time  or  transporting  it  to 
some  distance  must  needs  take  place,  care  must  be  taken  not 
merely  to  completely  exclude  any  access  of  air  to  it,  but  also  to 
entirely  remove  the  water  employed  in  taking  the  sample,  which 
would  exercise  a  solvent  action  on  some  of  the  constituents  of  the 
gas.  If  the  sampling  is  carried  out  without  contact  with  water, 
by  means  of  an  india-rubber  pump  and  a  dry  collecting  vessel, 
or  by  aspirating  it  through  the  same,  this  operation  must  be 
continued  long  enough  to  ensure  the  complete  expulsion  of  all  air. 

1  Some  of  these  are  described  and  illustrated  in  Winkler-Lunge,  pp.  17 
to  20. 


COLLECTING-VESSELS  15 

India-rubber  collecting  vessels  should,  as  a  rule,  be  avoided 
(cf.  supra,  Lunge  and  Harbeck,  p.  4),  even  if  their  inside 
surface  is  protected  by  a  coat  of  grease,  because  several  gases, 
especially  sulphur  dioxide  and  hydrogen,  are  diffused  through 
their  walls.  It  has  been  found,  however,  that,  for  instance, 
mixtures  of  oxygen,  nitrogen,  carbon  dioxide,  and  carbon 
monoxide  (that  is,  the  gases  produced  by  the  combustion  of 
fuel)  can  be  kept  unchanged  in  such  vessels  for  several  hours, 
but  not  till  the  next  day. 

Glass  collecting  vessels  (e.g.  that  shown  in  Fig.  2,  p.  6) 
should  be  provided  at  both  ends  with  tightly  closing  glass  taps, 
or  with  capillary  ends  which  are  sealed  by  the  lamp  after 
introducing  the  gas.  In  order  to  transfer  the  gas  afterwards 
to  a  gas-burette,  a  file  stroke  is  cautiously  made  on  each  of  the 
capillary  ends ;  narrow  india-rubber  tubes  are  slipped  over 
the  capillaries,  which  are  filled  with  water  and  closed  by  means 
of  glass  rods  or  pinchcocks.  Now  the  ends  are  broken  off 
within  the  india-rubber  tubes  by  pressure  from  without,  after 
connecting  one  of  them  with  the  gas-burette  (previously  filled 
with  water).  The  other  end  is  made  to  dip  into  a  vessel  also 
filled  with  water.  The  closing-rod  is  removed  below  the  water, 
and  the  water  contained  in  the  burette  is  run  off  so  that  it  is 
filled  with  the  gas,  the  place  of  which  in  the  collecting  tube  is 
taken  by  water.  Tread  well  (Quant.  Anal.,  p.  610)  describes  a 
similar  method  for  transferring  the  gas  from  the  glass  tubes 
to  a  burette. 

In  many  cases  if  the  analysis  can  be  carried  out  shortly 
after  collecting  the  gas,  it  is  not  necessary  to  close  the  collecting 
glass  tubes  by  sealing  the  capillary  ends  before  the  lamp ;  they 
may  be  closed  by  a  short  elastic  tube  provided  with  a  pinch- 
cock,  or  a  bit  of  glass-rod  with  rounded  ends,  by  well- 
ground-in  glass  taps. 

Where  for  gas  -  analytical  purposes  glass  stopcocks  are 
employed,  these  must  be  kept  tight  by  proper  lubrication. 
Dennis  (Gas- Analysis,  p.  115)  describes  for  this  purpose  the 
following  preparation,  which  does  not  deteriorate  on  keeping, 
does  not  work  out  at  the  ends  of  the  key,  and  gives  off  no 
hydrocarbon  vapour.  "  Place  in  an  evaporating  dish  twelve  parts 
of  vaseline  and  one  part  of  paraffin-wax.  Heat  this  mixture 
over  a  Bunsen  flame,  and  maintain  the  contents  of  the  dish 


16 


TECHNICAL  GAS-ANALYSIS 


at  a  temperature  that  will  keep  the  materials  fluid,  but  will 
not  cause,  the  mixture  to  emit  fumes.  Drop  in  successive 
portions  of  soft  black  rubber  clippings,  and  stir  the  mixture 
after  each  addition  until  the  rubber  is  completely  dissolved. 
After  about  nine  parts  by  weight  of  rubber  has  been  added, 

take  out  a  small  sample  of 
the  lubricant  on  the  end  of  a 
stirring-rod,  allow  it  to  cool, 
place  it  on  the  ball  of  the 
thumb,  squeeze  it  with  the 
end  of  the  middle  finger,  and 
then  rapidly  tap  the  finger 
upon  the  thumb  at  the  point 
covered  by  the  lubricant.  If 
on  this  treatment  the  lubri- 
cant forms  light,  feathery 
particles  that  float  off  in  the 
air  in  fine  flocks,  the  proper 
mixture  has  been  reached.  If 
the  lubricant  does  not  behave 
as  described,  stir  in  more 
rubber  and  test  again.  About 
ten  parts  by  weight  of  the 
rubber  will  usually  be  required 
for  the  above  amounts  of 
vaseline  and  paraffin.  In 
lubricating  a  glass  stopcock, 
the  key  and  barrel  should 
first  carefully  be  cleaned,  and 
then  the  thinnest  possible 
film  of  vaseline  be  rubbed 

FlGi  over  the  surface   of  the  key 

of  the  stopcock.  The  lubri- 
cant is  then  rubbed  over  the  key,  which  is  next  inserted  in 
the  barrel  and  turned  around  until  the  lubricant  is  evenly 
distributed  over  the  surface." 

Wempe  (Z.  angew.  Chem.y  1914,  i.  p.  216)  describes  a  collect- 
ing-pipe for  gases  without  a  tap,  and  another  with  a  glass  valve. 
For   collecting   and   transporting    larger   volumes   of  gases 
which  have  no  action  on   zinc,  Winkler   recommends   vessels 


MEASUREMENT  17 

made  of  zinc>  as  shown  in  Fig.  14.  They  are  cylinders,  50  cm. 
long  and  16  cm.  wide,  with  conical  ends,  5  cm.  long,  and  hold 
10  litres  of  gas.  They  terminate  at  each  end  in  necks  of 
15  mm.  diameter,  which  are  tightly  closed  by  soft  india-rubber 
plugs.  The  vessel  is  hung  in  a  stand  from  three  brass  chains 
fitted  at  the  top  in  a  ring,  and  can  thus  be  conveniently  carried 
by  hand  even  when  filled  with  water.  The  gas  sample  is 
collected  by  putting  the  vessel  in  the  proper  place  and  running 
the  water  out.  If  it  is  desired  to  produce  a  slow  or  specially 
regulated  outflow,  the  solid  bungs  are  replaced  by  bungs  fitted 
with  glass  tubes  and  provided  with  screw  pinchcocks.  Such 
vessels  are  employed  in  large  numbers  for  taking  samples  of 
the  pit  gases  in  the  Saxon  coal-pits,  and  sending  them  for 
analysis  to  the  Freiberg  Mining  Academy. 

For  collecting  the  gases  from  mineral  springs,  apparatus 
have  been  constructed  by  Ramsay  and  Travers  (Proc.  Roy.  Soc., 
1896,  p.  442),  by  Tiemann  and  Preusse  (Berl.  Ber.,  1879,  p. 
1768),  by  Henrich  (ibid.^  1908,  p.  4199),  by  Knud  and  Ruppin 
(Hempel's  Gasanal.  Methoden,  4th  ed.  1913,  p.  10). 

THE   MEASUREMENT   OF   GASES. 

The  volume  of  gases  can  be  found  either  by  directly 
measuring  it,  or,  in  some  cases,  by  titration  or  gravimetric 
analysis.  In  this  section  we  treat  only  of  the  direct  measuring 
of  the  gas  volume. 

The  tension,  and  therewith  the  volume  of  gases,  depends 
upon — 

ist.  The  pressure. 

2nd.  The  temperature. 

$rd.  The  state  of  moisture. 

These  conditions  may  be  very  different  to  begin  with,  and 
may  vary  during  the  analysis  even  from  one  observation  to 
another.  For  very  rapid  technical  estimations  of  the  con- 
stituents of  a  gas  these  differences  may  be  neglected ;  but  even 
for  many  technical  and  for  all  accurate  purposes,  the  gas 
volumes  must  be  reduced  to  fixed  conditions  called  the  "  normal " 
state,  viz.,  to  the  barometric  pressure  of  760  mm.  mercury,  to 
a  temperature  of  o°  C.,  and  (for  scientific  purposes)  to  a  state 
of  absolute  dryness.  For  technical  purposes  the  last-named 

B 


18  TECHNICAL  GAS-ANALYSIS 

correction  is  frequently  not  made.     The  expansion  by  heat  is 
•g-fs-  of  the  volume  of  the  gas  at  o°  for  each  degree  centigrade. 

All  these  corrections  are  embraced  in  the  following  formula, 
in  which  V  signifies  the  corrected  volume  ;  V  the  volume  observed 
at  the  barometric  pressure  B  ruling  at  the  time  of  the  observa- 
tion ;  t  the  temperature  of  the  gas  ;  and /the  tension  of  aqueous 
vapour  at  the  temperature  t  (as  shown  in  the  table  at  p.  25) : — 

.   Vx273x(B-/) 
(273  +  0  x  760  ' 

For  example,  we  have  found  the  gas,  saturated  with  moisture, 
to  occupy  at  738  mm.  pressure  at  20°  C,  a  volume  of  1000  c.c. 
Its  volume  in  the  dry  state  at  normal  temperature  and  pressure 
will  be  : — 

=    loco  x  2 73  x  (738 -i 7-4)   m   88       c>c. 
(273  +  20)  x  760 

Wendriner  (Z.  angew.  Chem.,  1914,  i.  p.  183)  gives  a  formula 
for  reducing  gas  volumes  to  the  normal  state  by  means  of 
logarithms  and  special  tables. 

Tables  for  the  reduction  of  the  volume  of  gases  to  normal 
temperature  and  pressure,  which  replace  the  use  of  the  above 
formula  by  a  simple  reading,  are  given  in  Lunge's  Technical 
Chemists'  Handbook,  1910,  pp.  38  to  52. 

This  reduction  to  the  "normal"  state  may  be  omitted  in 
technical  estimations  which  are  rapidly  performed,  since 
material  changes  of  pressure  and  temperature  need  not  be 
expected  in  such  cases.  Variations  of  the  barometric  pressure 
by  ±  i  mm.  change  the  volume  of  a  gas  by  +  i  per  cent. ; 
variations  of  the  temperature  by  ±  i°  C.  cause  a  change  of  ± 
0-3  per  cent. 

It  is  therefore  of  great  importance  to  keep  the  temperature  of 
a  laboratory  for  gas-analysis  as  uniform  as  possible.  Wherever  it 
is  possible,  a  room  with  its  window  looking  north  is  preferable. 

When  a  gas  is  estimated  by  titration  or  by  gravimetric 
analysis,  its  volume  is  at  once  calculated  in  the  corrected  state. 
If  one  of  the  gaseous  constituents  has  been  estimated,  say,  by 
titration,  and  another  volumetrically,  it  may  be  desirable  to 
calculate  the  volume  which  the  former  would  occupy  at  the 
then  existing  state  of  barometric  pressure  and  temperature,  and 


REDUCTION  TO  NORMAL  STATE 


19 


in  a  state  of  saturation  with  marsh.  The  following  formula 
serves  for  reducing  the  volume  of  a  gas  from  the  normal  state  to 
that  which  it  would  occupy  at  a  different  pressure  and  temperature, 
and  in  a  state  of  complete  saturation  with  moisture  :  — 


273(B-/) 


where  V,  V0,  /,  and  /have  the  same  meaning  as  supra. 

Apparatus  for  the  mechanical  reduction  of  the  volumes  oj 
gases  to  the  normal  state  without  ob- 
serving' the  barometer  and  thermometer. 
—  An  apparatus  for  this  purpose  was 
described  by  Barnes  (/.  Chem.  Soc., 
xxxix.  p.  463),  Vernon  Harcourt  in 
1883,  Kreusler  (Ber.,  1884,  p.  29). 
Winkler  (ibid.,  1885,  p.  2533)  and 
Lunge  (Chem.  Ind.,  1885,  p.  163)  have 
described  more  convenient  appara- 
tus for  the  same  purpose.  Lunge's 
apparatus  is  shown  in  Fig.  15.  An 
iron  stand  with  two  clamp  -  arms 
carries  two  perpendicular  glass  tubes, 
connected  at  the  bottom  by  a  thick 
india-rubber  tube  ;  one  of  these,  A, 
is  the  measuring-tube,  the  other,  B, 
the  "level-tube."  Tube  A  is  enlarged 
at  the  top  into  a  bulb  and  is  closed 
by  an  absolutely  tight  tap.  (Experi- 
ence has  shown  that  no  ordinary 
glass  taps  hold  tight  in  the  long 
run  ;  the  means  of  attaining  this  end 
will  be  described  later  on  in  connec- 
tion with  the  "gas-volumeter.")  A 
holds  exactly  100  c.c.  from  the  top 
to  the  zero  mark  on  the  stem.  The 
division  marked  on  the  cylindrical 
part  extends  from  the  zero  point  to 
5  c.c.  upwards  and  25  c.c.  below,  so  that  volumes  of  from  95  to 
125  c.c.  can  be  read  off  accurately  to  o-i  c.c.  These  two 


FIG.  15. 


20  TECHNICAL  GAS-ANALYSIS 

extreme  values  would  correspond  to  100  c.c.  air  under  normal 
conditions,  saturated  with  moisture,  when  brought  to  800  mm. 
barometric  pressure  and  o°  /  on  the  one  side,  or  to  700  mm. 
pressure  and  30°  t  on  the  other  side,  which  limits  embrace  all 
values  occurring  under  ordinary  circumstances.  Tube  A  is  held 
vertically  in  the  lower  clamp,  the  division  being  completely  in 
view.  The  level-tube  B  is  open  at  the  top,  which  is  protected 
by  a  dust-cover.  B  is  held  in  the  upper  clamp  of  the  stand, 
and  can  be  moved  upwards  or  downwards  by  means  of  a  screw- 
clamp.  It  holds  about  30  c.c. 

In  order  to  set  the  apparatus  once  for  all  for  permanent 
use,  the  air  contained  in  A  is  for  ordinary  purposes  of  technical 
analysis  saturated  with  moisture,  by  introducing  a  few  drops 
of  water.  (In  those  cases  where  the  gas  to  be  measured  is  in 
the  dry  state,  e.g.  the  nitric  oxide  given  off  in  the  testing  of 
nitrous  and  nitric  compounds  by  means  of  the  nitrometer,  to  be 
described  later  on,  the  reducing-instrument  is  adapted  to  this 
special  use  by  putting  in  a  drop  of  concentrated  sulphuric  acid, 
in  lieu  of  water,  and  making  the  subsequent  calculation 
accordingly.)  A  sufficient  quantity  of  mercury  is  poured  in 
through  B,  the  instrument  is  placed  into  a  room  of  even 
temperature,  with  a  barometer  and  thermometer,  and  after 
a  few  hours,  or  better  the  next  day,  both  of  the  latter  instru- 
ments are  read  off.  According  to  the  formula  given  on  p.  20, 
it  is  calculated  what  volume  100  c.c.  of  air,  assumed  to  be  in  the 
"  normal  "  state,  would  occupy  under  the  actually  existing  con- 
ditions. The  tap  at  the  top  of  A  being  left  open,  tube  B  is 
raised  or  lowered  to  the  point  where  the  mercury  level  in 
this  tube  indicates  precisely  the  calculated  volume,  and  the 
tap  is  now  closed  The  volume  of  air  thus  confined  increases 
or  decreases  with  every  change  of  external  pressure  and 
temperature,  exactly  in  the  same  ratio  as  other  gaseous  volumes 
present  in  the  same  room  and  intended  to  be  measured,  so 
that  the  "  normal "  volume  of  the  latter  can  be  calculated 
by  simple  proportion,  after  having  brought  the  mercury  in 
A  and  B  to  the  same  level  and  reading  off  the  volume  shown 
in  A. 

Lunge  (Chem.  Zeit.,  1888,  p.  821;  Z.  angew.  Chem.,  1890, 
p.  227)  has  described  a  modification  of  this  instrument  which 
yields  the  reduced  volume  by  a  simple  operation,  and  also  the 


GAS-VOLUMETER  21 

preparation  of  such  reduction-tubes  in  a  state  fit  for  carriage 
to  a  distance ;  but  these  modifications,  as  well  as  the  original 
instrument,  have  become  obsolete  by  his  invention  of  the  "  gas- 
volumeter,"  described  below. 

The  correction  for  pressure  and  temperature  may  be  avoided 
in  cases  where  mercury  is  employed  as  confining  liquid  by 
the  employment  of  a  Compensator^  that  is  a  glass  vessel  con- 
nected with  the  measuring  apparatus  by  a  capillary,  in  which 
there  is  a  minute  column  of  liquid.  Any  alterations  of 
temperature  and  pressure  influence  the  gas  volume  equally 
both  in  the  compensator  and  the  gas-burette,  so  that  no 
corrections  are  required  if  the  pressure  is  made  equal  in  both 
apparatus.  Such  an  apparatus  has  been  described  by  Petterson 
(Z.  anal.  Chem.,  xxv.  p.  467),  and  improved  by  Hempel  and 
Drehschmidt;  we  shall  mention  it  later  on  in  connection 
with  Drehschmidt's  methods  for  gas-analysis.  Another  such 
"compensator"  has  been  constructed  by  Borchers  (Ger.  P. 
259044). 

An  apparatus  for  the  automatic  elimination  of  the  influence 
of  temperature  in  gas-balances  has  been  constructed  by  Knoll 
(Ger.  P.  247738 ;  /.  Gasbeleucht,  1913,  p.  407).  On  the  beam  of 
the  balance  or  in  the  balance  case  two  vessels  are  fixed,  one 
which  is  closed  and  entirely  filled  with  mercury ;  the  other 
vessel  is  open,  and  but  partially  filled  with  mercury. 

Lunge's  Gas-volumeter  (Lunge,  Berl.  Ber.,  1890,  p.  440;  1892, 
p.  3157;  Z.  angew.  Chem.,  1890,  p.  130;  1891,  p.  410;  1892, 
p.  677)  for  the  first  time  realised  the  task  of  doing  away  with 
all  calculations  for  reducing  a  gas  volume  to  the  "  normal  state," 
that  is  usually  to  o°  C.  and  760  mm.  pressure,  either  in  the 
completely  dry  state  or  when  saturated  with  moisture,  by 
means  of  a  mechanical  operation  carried  out  in  a  minimum 
of  time  and  with  a  maximum  of  accuracy,  without  any 
recourse  to  calculations  or  tables.  And  this  is  done  not 
merely  for  relative  measurements,  that  is  for  comparing 
various  gas  volumes  with  the  initial  volume  of  a  gas  to  be 
analysed,  but  for  absolute  measurements,  such  as  are  re- 
quired for  the  gas-volumetric  analysis  of  liquid  or  solid 
substances. 

The  fundamental  idea  of  this  process  is  the  following: — If  a 
certain  quantity  of  air  contained  in  a  "reduction-tube"  is  by 


22  TECHNICAL  GAS-ANALYSIS 

means  of  a  "  level-tube  "  placed  under  such  pressure  that  it 
occupies  the  same  volume  as  it  would  occupy  at  o°  C.  and  760 
mm.  barometric  pressure,  and  if  precisely  the  same  pressure  is 
exercised  on  another  unknown  quantity  of  a  gas,  the  latter 
must  equally  occupy  the  volume  corresponding  to  o°  C.  and  a 
pressure  of  760  mm.  This  purpose  is  attained  if,  first,  the  level- 
tube  is  placed  at  such  a  height  that  the  air  contained  in  the 
reduction-tube  is  reduced  to  the  volume  corresponding  to  the 
"  normal "  state ;  if,  second,  the  same  pressure,  by  the  applica- 
tion of  a  ~l~-pipe,  is  made  to  act  upon  the  tube  or  other  vessel 
containing  the  gas  to  be  measured ;  and  if,  third,  the  level  of 
the  mercury  in  the  last  tube  or  vessel  is  exactly  the  same  as 
in  the  "  reduction-tube." 

This  contrivance  may  be  applied  to  a  gas-burette,  or  any 
other  apparatus  in  which  gases  are  to  be  measured,  more 
particularly  also  to  the  "  nitrometer "  to  be  described  later  on 
(for  which  purpose  it  was  first  employed).  We  show  it  in  Fig. 
1 6  in  connection  with  a  gas-burette  A ;  B  is  the  "  reduction  - 
tube  "  and  C  the  "  level-tube." 1  They  are  all  joined  by  very 
strong  elastic  tubes  to  a  three-way  pipe  (T~pipe)  D,  and  they 
can  be  made  to  slide  upwards  and  downwards  in  strong  clips. 
(All  these  parts  are  here  shown  in  their  simplest  form  ;  they 
have  been  considerably  improved  in  shape  later  on.)  The  gas- 
burette  A  is  generally  made  to  hold  50  c.c.,  divided  in  01  c.c., 
or  else  it  holds  about  150  c.c.,  the  upper  90  or  100  c.c.  being 
formed  as  a  bulb,  and  the  graduation  beginning  only  at  90  or 
100  c,c.,  and  reaching  down  to  the  bottom.  Or  else  this  tube 
has  a  bulb  in  the  middle,  and  is  graduated  from  o  to  30,  and 
again  from  100  to  150  c.c.,  so  as  to  admit  of  measuring  either 
small  or  large  volumes  of  gas  without  unduly  lengthening  the 
tube.  Tube  B  is  made  exactly  like  tube  A  in  the  gas-reduction 
apparatus  (Fig.  15,  p.  19),  and  is  filled  with  exactly  100  c.c.  of  air, 
calculated  for  760  mm.  pressure  and  oc  C.,  precisely  as  stated 
in  that  place.  This  air  must  be  either  saturated  with  moisture 
by  previously  introducing  a  few  drops  of  water,  or  else 
completely  dried  by  means  of  a  drop  of  concentrated  sulphuric 
acid.  In  the  first  case  the  instrument  is  best  adapted  for  the 

1  The  tubes  E  and  F  serve  for  the  analysis  of  nitrous  vitriol, 
to  be  described  in  a  later  chapter,  and  need  not  be  noticed  in  this 
place. 


GAS-VOLUMETER 


23 


measurement  of  moist  gases,  in  the  second  for  that  of  dry  gases. 
It  is  set  once  for  all  by  observing  the  state  of  the  thermometer 
and  barometer,  calculating  the  volume  which  100  c.c.  of  dry  (or 


FJG.  16 


moist)  air  would  occupy  under  the  conditions  observed  by 
means  of  the  formula  given  in  p.  1 8,  setting  the  level  of 
mercury  at  the  corresponding  place,  and  shutting  the  stopcock 
at  the  top.  If  this  stopcock  shuts  air-tight,  the  reduction-tube 


TECHNICAL  GAS-ANALYSIS 


holds  for  ever  a  volume  of  air,  corresponding  to  100  c.c.  at  o° 
and  760  mm.  pressure.  Glass  taps,  securing  a  permanently  tight 
closing  fit  have  been  constructed  by  Gockel  (Z.  angew.  Chem.y 
1910,  pp.  961  and  1238;  they  are,  for  instance,  manufactured 
by  Alt.  Eberhard  and  Jaeger,  at  Ilmenau).  Or  else  tube  B,  in 

^         lieu  of  a  glass  tap,  ends  at  the  top  in  a  capillary, 

which  is  sealed  by  a  flame  after  setting  the  tube 
at  the  proper  volume. 

The  level-tube  C  is  best  shaped  as  shown 
in  Fig.  17,  in  order  to  save  mercury. 

In  order  to  put  the  reduction-tube  into  its 
working  state,  the  state  of  the  barometer  B, 
as  well  as  that  of  a  thermometer  placed  beside 
the  tube  /  is  observed;  and  it  is  calculated 
which  volume  100  c.c.  of  o°  and  at  760  mm. 
pressure  would  occupy  at  the  temperature  t 
and  the  barometric  pressure  B.  If  the  instru- 
ment is  to  be  set  for  the  moist  state,  the 
tension  of  aqueous  vapour  at  the  temperature 
/=/  is  introduced.  The  calculation  is  made 
either  by  the  formulae  : — 


0 


for  dry  gases : 

Vi   - 
for  moist  gases : 


v,  = 


273B 


FIG.  17. 


or  else  from  Tables  20  and  21  in  Lunge's 
Technical  Chemists'  Handbook,  1910,  pp.  38  to  52.  Now,  the 
top  of  the  reduction-tube  still  being  open,  the  level-tube  is 
placed  at  the  point  indicated  by  V,  which  of  course  will  be 
always  above  100  c.c. ;  the  stopcock  is  then  closed  (or  the 
capillary  end  sealed  up),  and  the  instrument  is  now  fit  for 
use. 

The  following  table  shows  the  amount  of/,  viz.,  the  tension 
of  aqueous  vapour  in  millimetres  of  mercury  at  the  tempera- 
tures likely  to  occur  in  a  chemist's  laboratory,  viz.,  between  10° 


CORRECTION  FOR  AQUEOUS  VAPOUR 


25 


and  30°  C.  More  detailed  tables,  extending  from  —20°  to  230° 
C,  also  for  Fahrenheit  degrees,  are  given  in  Lunge's  Technical 
Chemists'  Handbook,  Nos.  23  to  25,  pp.  54  to  58  : — 

TABLE  I. — Tension  of  Aqueous  Vapour. 


Temperature. 
°C'. 

Pressure, 
mm.  Hg. 

Temperature. 
°C'. 

mm. 
°C'. 

+  10 

9-126 

21 

18-505 

II 

9756 

22 

I9-675 

12 

10-421 

23 

20-909 

13 

IT-ISO 

24 

22-211 

H 
15 

11-882 
12-677 

3 

23-582 
25-026 

16 

I3-5I9 

27 

26-547 

17 

14.409 

28 

28-148 

18 

I5-35I 

29 

29-832 

19 

16-345 

30 

3I-602 

20 

17-396 

According  to  whether  it  is  more  frequently  required  to 
measure  gases  in  the  dry  state  (e.g.  in  the  nitrometric  analysis 
of  nitrous  vitriol,  of  nitrates,  of  explosives,  etc.)  or  in  the 
moist  state  (e.g.  in  the  usual  technical  analysis  of  fire-gases, 
producer-gases,  etc.),  the  reduction-tube  will  be  set  for  the  dry 
or  the  moist  state.  It  is,  however,  quite  possible  to  employ 
that  tube,  when  set  for  dry  gases,  to  measure  gases  in  the 
moist  state,  and  vice  versa.  If,  for  instance,  dry  gases  are  to 
be  measured  with  a  moist  reduction-tube,  the  temperature  is 
observed,  the  corresponding  aqueous  vapour  tension  f  is  taken 
from  the  table  just  given,  and  the  mercury  in  the  gas-measuring 
tube  A  is  set  at /mm.  higher  than  in  the  reduction-tube,  which 
had  been  set  at  100  c.c.  This  is  a  very  simple  matter,  as  the 
gas-tube  A  is  chosen  of  such  width  that  each  cubic  centimetre 
occupies  almost  exactly  a  height  of  10  mm.,  because  in  this 
case  it  is  not  necessary  to  apply  a  measuring-ruler.  If,  vice 
versa,  a  dry  reduction-tube  is  to  be  employed  for  moist  gases, 
the  mercury  in  the  measuring-tube  must  be  set  by  f  mm. 
lower  than  in  the  reduction-tube,  where  it  is  always  set  at 
100  c.c. — Or  else,  in  order  to  measure  a  dry  gas  in  A  with  a 
moist  reduction-tube,  it  is  first  put  into  the  moist  state  by 
introducing  a  drop  of  water,  which  is  most  easily  done  before 
allowing  the  gas  to  enter  into  A.  For  the  inverse  case,  a 


26 


TECHNICAL  GAS-ANALYSIS 


moist  gas  is  dried  in  A  by  a  drop  of  concentrated  sulphuric 
acid.  In  either  case  care  must  be  taken  not  to  allow  the  liquid 
to  project  above  the  mercury  meniscus. 

Reduction-tubes  readily  filled  for  Sales. — The  construction  of 
reduction-tubes  containing  the  exact  volume  of  100  c.c.  under 
standard  conditions,  and  arranged  in  such  manner  that  they  can 
be  kept  in  stock  and  sent  out  to  customers  by  dealers  in 
chemical  apparatus,  has  been  described  by  Lunge  (Z.  angew. 
Chem.)  1890,  p.  228)  and  by  Rey  (ibid.>  p.  229);  but  we  merely 
refer  to  this,  as  difficulties  have  turned  up  in  the  practical 
application  of  such  tubes. 

As  stated  above,  the  connection  of  the  tubes  A,  B,  and  C,  in 
Fig.  1 6,  p.  23,  is  effected  by  means  of  a  T-shaped  pipe,  to 


FIG.  18. 


FIG.  19. 


which  they  are  joined  by  very  thick  india-rubber  tubing.  Such 
tubing,  say  of  an  external  diameter  of  13-5  mm.  and  a  width  of 
4-5  mm.,  perfectly  well  stands  the  pressure  of  the  mercury  with- 
out blowing  out,  and  even  without  the  necessity  of  fixing  it  to 
the  glass  by  means  of  wire,  especially  if  the  ends  of  the  glass 
tubing  are  a  little  thickened.  Elastic  tubing  of  the  just- 
mentioned  size  can  be  easily  drawn  over  glass  tubes  of  an 
outside  diameter  of  10  mm.,  or  even  a  little  more. 

The  tubes  A,  B,  and  C  are  held  in  strong  spring  clamps  by 
friction,  in  such  manner  that  they  can  be  moved  upwards  or 
downwards,  but  do  not  descend  by  themselves.  Such  spring 
clamps  sometimes  fail  to  act  properly  after  a  time.  This  draw- 
back is  avoided  by  employing  the  double-screw  clamps  shown 
in  Figs.  1 8  and  19,  as  supplied  by  C.  Desaga  in  Heidelberg,  and 
others. 


GAS-VOLUMETER  27 

A  cast-iron  fork  carries  in  front  two  cork-lined  clamps;  a 
smaller  one,  a,  for  the  reduction-tube  (to  be  held  below  the  100 
c.c.  mark),  and  a  larger  one,  ^,  for  the  level-tube.  This  fork  is 
held  on  the  stand  by  an  ordinary  clamp  c,  or  one  strengthened 
by  a  spring  as  shown  in  Fig.  19.  By  this  fork-clamp  the 
reduction-tube  and  the  level-tube  are  combined  to  a  set, 
movable  in  common  upwards  or  downwards.  When  the  gas- 
analytical  operation  has  been  finished,  the  set  is  put  approxi- 
mately at  the  level  of  the  mercury  in  the  gas-measuring  tube ; 
the  level-tube  is  moved  in  its  clamp  b,  in  such  manner  that  the 
mercury  in  the  reduction-tube  comes  exactly  up  to  the  mark 
100  c.c.,  and  the  fork-clamp,  together  with  its  two  tubes,  is 
moved  through  the  clamp  c,  until  the  mercury  in  the  reduction- 
tube  and  the  gas-measuring  tube  is  exactly  on  the  same  level. 
All  this  can  be  done  in  a  few  seconds,  and  much  more  easily 
than  by  means  of  separately  moving  spring  clamps. 

Since  a  difference  of  only  i°  corresponds  to  a  variation 
of  0-3  per  cent,  in  the  gas  mixture,  the  gas-volumeter  should 
stand  in  a  room  of  uniform  temperature  and  free  from  draughts. 

Manipulation  of  the  Gas -volumeter. — Suppose  that  a  gas- 
analytic  or  gas-volumetric  operation  has  been  carried  out  in 
tube  A  (Fig.  16,  p.  23).  The  reading  of  the  gas  volume  is,  in  this 
case,  not  performed  in  the  ordinary  manner  after  putting  the 
mercury  in  A  and  C  on  the  same  level.  Only  in  such  cases 
where  a  special  side-bottle  ( "  agitating  vessel "  )  has  been  used — 
e.g.  for  nitrogen  estimations  by  the  bromine-soda  method,  for 
the  hydrogen  peroxide  methods,  for  carbon-dioxide  estima- 
tions, etc. — it  is  necessary  at  first  to  place  the  levels  in  A  and  C 
at  the  same  heights,  in  order  to  bring  the  gas  in  A  to  the 
atmospheric  pressure  ruling  at  the  moment,  whereupon  the 
top  of  A  is  closed,  without  reading  the  gas-volume  in  that  tube. 
If  the  gas  has  been  evolved  in  A  itself,  or  conveyed  into  that 
tube  from  another  apparatus,  the  just-described  operation  does 
not,  of  course,  come  into  question.  The  proper  reading  in  A 
only  takes  place  after  placing  the  three  tubes  in  such  manner 
that  the  levels  of  the  mercury  in  A  and  B  are  at  the  same 
height,  and  that  in  B  is  at  the  same  time  on  the  100  c.c.  mark. 
In  that  case  the  gases  both  in  A  and  B  are  under  such  a  pressure 
that  the  reading  of  the  volume  indicates  the  volume  which  they 
would  occupy  at  o°  and  760  mm.  This  condition,  of  course,  has 


28  TECHNICAL  GAS-ANALYSIS 

been  once  for  all  established  in  B,  and  it  now  exists  also  in  A, 
since  the  temperature  and  pressure  (caused  by  the  position  of 
C)  are  the  same  as  in  B. 

The  setting  of  the  tubes  at  the  proper  points  is  most  easily 
and  quickly  done  in  the  following  way : — Tube  A  is  fixed  in 
the  clamp,  B  and  C  are  lifted  up,  but  not  equally ;  tube  C 
must  be  placed  so  much  higher  that  the  mercury  in  B  rises  to 
the  mark  100.  Now  B  and  C  are  simultaneously  moved 
downwards  in  their  clamps,  in  such  manner  that  their  mutual 
distance  remains  the  same  until  the  mercury  level  in  B,  that 
is  the  mark  100,  is  at  the  same  level  as  the  mercury  in  A. 
This  simultaneous  movement  is  not  easily  performed  quite 
equally,  but  it  can  be  at  once  completely  corrected  by  a  little 
shifting  of  the  position  of  B.  This  double  setting  takes  only 
a  few  seconds  more  time  than  the  ordinary  setting  of 
the  level-pipe  for  the  gas-burette.  Of  course  the  placing  of  the 
mercury  in  A  and  B  on  the  same  level  can  be  facilitated  in 
the  same  way  as  in  all  similar  cases,  by  sighting  at  the  top 
of  a  wall  or  a  window  frame,  or  by  a  special  straight-edge 
provided  with  a  spirit-level  as  constructed  by  Lunge  (Ber.y 
1891,  p.  3948). 

The  simultaneous  moving  of  two  tubes,  fitted  with  mercury, 
is  rather  irksome  if  the  spring  clamps  hold  them  tightly  (as 
they  ought  to  do).  This  drawback  is  completely  avoided 
by  employing  the  double  screw  clamp  shown  in  Figs.  18  and  19, 
p.  26. 

In  those  cases  where  some  other  liquid,  apart  from  mercury, 
is  introduced  into  the  gas  measuring-tube,  its  pressure  must 
of  course  be  taken  into  account  as  well.  Thus,  for  instance, 
for  the  estimation  of  nitrogen  by  the  method  of  Dumas,  a 
special  mark  is  made  on  the  reduction-tube  below  the  mark 
100,  corresponding  to  a  tenth  of  the  height  of  the  potash 
solution  contained  in  the  gas  measuring-tube.  If  the  levels 
before  reading  are  set  in  such  manner  that  the  mercury  in 
the  reduction-tube  stands  at  100,  but  in  the  gas  measuring- 
tube  on  the  same  plane  as  the  mark  made  below  100,  the 
height  of  the  column  of  potash  liquor  is  thereby  compensated. 

It  will  be  now  clear  that  the  employment  of  the  gas- 
volumeter  does  away  with  the  necessity  of  reading  the  thermo- 
meter and  barometer,  as  well  as  that  of  making  any  calculations 


GAS-VOLUMETER  29 

of  the  reduced  volumes,  whether  by  means  of  the  afore-given 
formulae  or  by  special  tables  ;  the  gas  volumes  are  at  once  read  in 
a  state  reduced  to  the  "  normal "  conditions.  Only  as  remarked 
on  p.  24,  according  to  the  nature  of  the  analytical  operation, 
the  reduction-tube  must  be  arranged  either  for  dry  or  for 
moist  gases. 

The  principle  of  the  gas-volumeter  has  been  applied  also  to 
the  exact  estimation  of  carbon  dioxide  in  carbonates,  and  to 


FIG.  20. 


FIG.  21. 


that  of  carbon  in  iron  and  steel  (Lunge  and  Marchlewski, 
Z.  angew.  Ckern.,  1891,  pp.  229  and  412)  ;  but  we  cannot  discuss 
this  here,  and  merely  show  the  decomposition  flasks  constructed 
for  that  purpose,  Figs.  20  and  21,  which  admit  of  heating  the 
contents.  The  shape  shown  in  Fig.  20  avoids  the  use  of  cork 
or  india-rubber,  but  is  more  fragile  than  the  shape  Fig.  21. 


FIG.  22. 


Fig.  22  shows  the  combination  of  the  gas-volumeter  (or  of 
any  other  gas-measuring  apparatus)  with  an  agitating  bottle  for 


30  TECHNICAL  GAS-ANALYSIS 

the  estimation  of  carbon  dioxide,  for  the  estimation  of  nitrogen 
in  ammonium  salts  or  urea  by  means  of  brominated  soda 
for  the  analysis  of  peroxide,  permanganates,  manganese  ore, 
hypochlorites,  etc.,  to  be  described  in  a  later  chapter. 

Bodlander  (Z.  angew.  Chem.,  1894,  p.  425),  under  the  name 
of  "Baroscope,"  describes  an  instrument  for  calculating  the 
weight  of  the  gas  in  a  burette  from  its  pressure. 


MEASURING   APPARATUS    FOR   GASES. 

It  is  hardly  necessary  to  point  out  that  all  apparatus  for 
measuring  gases  must  be  correctly  graduated.  Mostly  the 
graduation  indicates  the  volume  in  cubic  centimetres,  but  its 
correctness  must  be  checked  by  calibrating,  either  by  the 
maker  (who  thereby  undertakes  a  guarantee  for  it),  or  by  the 
user.  In  gas-analysis  proper  it  is  usually  sufficient  if  the 
volumes  indicated  on  the  burettes,  etc.,  are  equal  amongst  each 
other;  but  for  the  gas-volumetric  testing  of  liquids  or  solids 
the  volumes  indicated  must  show  the  real  cubic  centimetres, 
since  the  volume  of  the  gas  given  off  in  the  operation  is  utilised 
for  calculating  a  weight  therefrom. 

The  first  consideration  is  always  with  regard  to  the  nature 
of  the  confining  liquid.  In  most  cases  mercury  is  on  principle  the 
most  suitable  liquid  for  this  purpose,  since  most  gases  do  not 
act  upon  it  (of  course  some  gases,  as  chlorine  and  bromine 
vapour,  do  so  very  strongly),  nor  are  they  soluble  in  it,  and 
since  it  does  not  at  all  adhere  to  the  glass  like  water,  or  aqueous 
liquids,  or  even  petroleum.  But  for  technical  gas-analysis, 
wherever  possible,  water,  or  sometimes  an  aqueous  solution  of 
common  salt,  is  used  as  confining  liquid,  not  merely  or  even 
principally  on  account  of  the  expense  of  the  mercury,  but 
because  the  construction  of  the  apparatus  is  often  greatly 
facilitated  thereby. 

Pfeiffer  (Lunge  and  Berl's  Chem.  techn.  Unt.  Meth.,  1911,  iii. 
p.  252)  recommends,  in  order  to  recognise  a  contamination  of 
the  confining  water  by  previously  employed  alkaline  absorbents, 
to  add  to  it  a  little  hydrochloric  acid  (20  c.c.  normal  HC1  to 
i  litre),  methyl  orange,  also  a  little  (0-5  g.)  sodium  salicylate,  to 
prevent  the  development  of  fungi. 

The  same  author,  in  order  to  promote  the  running  off  of  the 


MEASURING-APPARATUS 


31 


water  from  the  glass  sides  of  the  apparatus  and  the  formation 
of  a  clear  meniscus,  previously  rinses  the  vessels  with  a  mixture 
of  strong  sulphuric  and  nitric  acid. 

The  nature  of  the  confining  liquid  also  influences  the 
meniscus-correction  which  is  not  merely  different  for  different 
liquids,  but  which  must  also  be  taken  into  consideration  when 
weighing  water  or  mercury  into  such  vessels  which  in  actual  use 
are  in  an  inverted  position,  the  closed  end  then  being  at  the 
top.  Gockel  justly  points  out  that  gas-measuring  apparatus 
ought  to  be  marked,  e.g.  "  corrected  for  H2O,"  or  "  corrected  for 
Hg  dry,"  or  "  Hg  wet"  (Ghent.  Zeit.,  1902,  xxvi.  p.  159).  We 
shall  treat  of  this  below. 

With  respect  of  the  use  of  water  as  confining  liquid,  the 
solubility  of  gases  in  water  must  be  kept  in  view.  The  following 
table  shows  the  absorption  coefficients  of  various  gases,  that  is 
the  volume  of  gas  absorbed  by  water  of  different  temperatures, 

TABLE  1 1. — Solubility  of  Gases  in  Water. 


10°. 

15°. 

20°. 

25°. 

30°. 

35°. 

Oxygen  . 

0-038 

0-034 

0-031 

0-028 

C-026 

0-024 

Hydrogen 

0-020 

0-019 

O-Ol8 

0018 

0-017 

0017 

Nitrogen 

O-O2G 

0-018 

0016 

0-015 

0-014 

0-013 

Chlorine 

3-095 

2.635 

2-260 

1.985 

1-769 

1-575 

Carbon  monoxide 

0-028 

0-025 

0-023 

O-O2  1 

0-020 

0019 

Carbon  dioxide 

I.IQ4 

I-OI9 

0-878 

0-759 

0-665 

0-592 

Hydrogen  sulphi  le 

3-520 

3-056 

2-672 

... 

Ammonia 

910-4 

802-4 

710-6 

634-6 

... 

... 

Sulphur  dioxide 

56-65 

47-28 

39-37 

32-79 

27-16 

22-49 

Methane         . 

0-042 

0-037 

0-033 

0-030 

0028 

0-025 

Ethylene 

0«l62 

0-139 

0-122 

0-108 

0-098 

... 

Propylene 

0-230 

0-237 

0-221 

... 

... 

Acetylene 

1-31 

I-I5 

1-03 

o-93 

0.84 

... 

Atmospheric  air 

0-023 

0-020 

0-019 

0-017 

0-016 

0-015 

reduced  to  o°  C.  and  760  mm.  pressure,  if  the  gas  itself  is 
under  a  pressure  of  760  mm.  These  values  are  taken  from 
Bunsen  (Gasom.  Methoden,  2nd  ed.  p.  384)  ;  Winkler  (Ber., 
xxiv.  pp.  99,  3606,  3609)  ;  Landolt-Bornstein-Meyerhoffer,  3rd 
ed.  p.  599  ;  Bohr  and  Bock  (Wiedem.  Ann.,  xliv.  p.  318) ;  Than 
(Ann.,  cxxiii.  p.  187).  A  more  detailed  table  of  the  solubility  of 
gases  in  water,  extending  from  o°  to  100°,  is  given  in  Lunge's 
Technical  Chemists'  Handbook  (1910),  pp.  20  to  23. 


32 


TECHNICAL  GAS-ANALYSIS 


We  see  from  this  that  water  dissolves  so  much  ammonia, 
sulphur  dioxide,  and  chlorine  that  it  cannot  be  employed  as 
confining  liquid  in  the  presence  of  these  gases.  Its  dissolving 
power  for  carbon  dioxide,  acetylene,  propylene,  and  ethylene  is 
also  considerable;  if  these  are  present,  the  confining  water 
should  be  previously  shaken  up  with  another  quantity  of  the 

gas  to  be  examined.  Especially  in 
the  analysis  of  gaseous  mixtures  con- 
taining a  high  percentage  of  these 
gases  their  solubility  in  water,  as  well 
as  that  of  atmospheric  air,  must  be 
taken  into  consideration  (cf.  Stock 
and  Nielsen,  Ber.,  1906,  p.  3889). 

Contrivances  for  a  Correct  Reading 
of  the  Level  of  the  Liquid. — The  read- 
ings in  the  case  of  aqueous  confining 
liquids  are  taken  at  the  lowest  point 
of  the  meniscus,  where  the  coinci- 
dence with  one  of  the  marks  of  the 
graduation  can  be  clearly  recognised. 
Perfectly  exact  readings  are  taken 
by  means  of  a  magnifying  glass,  or 
with  even  more  certainty  through  the 
telescope  of  a  cathetometer,  Fig.  23, 
such  as  serve  for  accurate  observations 
of  the  barometer  and  thermometer. 
The  telescope  slides  up  and  down  on 
a  triangular  brass  column,  and  can 
be  easily  adjusted  in  any  place  by  a 
rack  and  pinion.  The  observations 
are  best  made  from  a  distance  of  2 
or  3  metres. 

This  instrument  is  hardly  ever  used  in  technical  gas- 
analysis,  but  for  this  as  well  the  mistakes  must  be  avoided 
which  are  caused  by  not  holding  the  eye  exactly  on  the  level  of 
the  meniscus.  Such  mistakes  cannot  occur  where  the  meniscus 
exactly  coincides  with  a  circular  mark  of  the  division,  running 
right  round  the  tube,  but  this,  of  course,  is  not  the  ordinary  case. 
The  "  floats,"  which  are  employed  in  the  ordinary  burettes  for 
volumetric  analysis  of  liquids  and  solids,  cannot  be  used  in 


FIG.  23. 


MEASURING  APPARATUS 


33 


gas-volumetric  apparatus,  and  there  are  certain  drawbacks 
connected  with  them  even  in  their  proper  sphere  (Kreltling, 
Z.  angew.  Chem.,  1900,  pp.  829  and  990 ;  1902,  p.  4). 

An  excellent  contrivance  for  avoiding  the  mistakes  in 
reading  burettes  is  that  described  by  Dr  H.  Gockel  in  Chem. 
Zeit.,  xxvii.  p.  1036,  by  the  name  of  Visierblende  (say, 
sighting- clamp) ,  and  shown  in  Fig.  24  in  its  application  both 
for  water  and  mercury.  The  sighting-clamp  is  placed  on  the 
burette  2  or  3  mm.  below  the  lowest  point  of  the  water 
meniscus,  or  above  the  top  of  the  mercury  meniscus,  and 


Meniscus 


Hq.  Meniscus 


FIG.  24. 


owing  to  the  shape  adopted  by  Gockel  one  and  the  same  clamp 
can  be  applied  to  tubes  of  from  9  to  20  mm.  diameter.  This 
black  clamp  produces  a  very  sharp,  black  limiting-line.  The 
parallax  fault  in  reading  is  avoided  by  the  fact  that  the  opening 
of  the  clamp  is  exactly  at  a  right  angle  to  its  horizontal  level, 
and  small  metal  discs  screwed  on  secure  the  fact  that  on 
opening  and  shutting  the  clamp  its  movement  always  takes 
place  in  the  same  plane.  Hence,  in  order  to  avoid  the  parallax 
fault,  the  eye  need  only  be  placed  at  such  a  height  that 
the  front  and  back  edge  line  of  the  clamp  coincide.  Gockel's 
sighting-clamp  is  doing  excellent  service  in  many  laboratories. 

Very  good  service  in  reading  the  levels  is  also  done  by 
employing  a  straight-edge,  provided  with  a  spirit-level,  as 
described  by  Lunge  in  Berl.  Ber.,  1891,  p.  3948. 


ADJUSTMENT   OR  CALIBRATION   OF  GAS- 
MEASURING   APPARATUS. 

Here  we  must  distinguish  between  apparatus  for  gas- 
analysis  proper,  where  only  relative  measurements  are  required, 
and  apparatus  for  gas-volumetric  analysis,  where  the  absolute 

c 


34  TECHNICAL  GAS-ANALYSIS 

quantity  of  the  gas  must  be  ascertained  (v.  supra,  p.  30).  We 
must  also  consider  whether  the  gas  is  to  be  confined  by  water, 
or  by  mercury  (in  the  case  of  nitrometers  the  confining  liquid 
is  sulphuric  acid),  and  we  must  also  take  the  meniscus  correction 
for  the  confining  liquids  into  account,  in  case  the  readings  are 
made  in  places  of  unequal  diameters  of  the  tubes. 

The  capacity  of  gas-burettes,  etc.,  intended  to  hold  exactly 
loocc.  or  any  other  definite  volume  between  two  glass  stop- 
cocks, such  as  Winkler's  burette,  is  hardly  ever  correct,  and 
the  actual  capacity  should  always  be  determined  and  the 
corrected  value  marked  on  the  burette ;  it  should  further  be 
noted  for  which  point  of  the  meniscus  the  reading  has  been 
calibrated,  and  whether  the  meniscus  correction  has  been  made 
for  water  or  for  mercury  (see  below). 

Prescriptions  for  ascertaining  the  volume  capacities  of 
gas -analytical  apparatus  have  been  given  by  Bunsen  (Gasom. 
Methoden,  2nd  ed.  pp.  55  et.  seq.}\  Berthelot  ( Traiti  pratique  de 
r analyse  des  gaz.,  1906,  pp.  215  to  217);  Gockel  (Chem.  Zeit.^ 
1902,  p.  195  ;  Z.f.  Chem.  App.  Kunde,  1907,  p.  305);  Schloesser 
and  Grimm  (eodem  loco,  1907,  p.  201).  The  last-mentioned 
paper,  which  is  based  on  the  researches  made  by  the  German 
Normal-Eichungskommission,  will  be  especially  taken  into 
consideration. 

We  first  quote  the  table  (p.  35)  they  give  for  the  meniscus 
corrections  for  water  and  mercury,  which  give  these  values  both 
in  cubic  centimetres  and  in  milligrams,  viz.,  as  the  height  of 
a  cylinder  of  the  diameter  of  the  tube  in  question. 

Calibration. — According  to  Schloesser  and  Grimm  the 
calibration  of  gas-analytical  apparatus  is  carried  out  in  the 
following  manner  (principally  founded  on  the  prescriptions  of 
the  Imperial  Normal-Eichungskommission)  : — 

I.  In  the  case  working  with  liquids  adhering  to  the  glass, 
mostly  water,  and  of  apparatus  which  during  the  calibration 
are  in  the  same  position  as  in  actual  use,  the  calibration  is 
carried  out  in  the  same  way  as  for  volumetric  apparatus 
generally.  The  water  is  weighed  in  small  stoppered  weighing- 
bottles  on  an  ordinary  analytical  balance.  Its  temperature 
must  be  taken  with  a  correct  thermometer  to  within  ±  01° 
(this  is  sufficient  for  all  cases,  although  the  German  Normal- 
Eichungskommission  goes  to  ±  001°).  The  normal  tempera- 


MENISCUS  CORRECTIONS  35 

TABLE  III. — Meniscus  Corrections  for  Mercury  and  Water. 


Mercury. 

Water. 

Diameter 

Correction. 

Correction. 

Diameter 

mm. 

In  c.c. 

In  mm. 

In  c.c. 

In  mm. 

of  tube, 
mm. 

I 

o-oor 

0-76 

2 

2                      54 

3 

3 

40 

0-006 

0-85 

3 

4 

4 

32 

10 

*0 

4 

5 

0006 

o-33 

0-015 

0-76 

5 

6 

12 

41 

22 

77 

6 

7 

2O 

53 

30 

78 

7 

8 

29 

S8 

41 

81 

8 

9 

38 

60 

53 

8? 

9 

10 

0-04S 

0-61 

0-067 

0-85 

10 

| 

ii 

57 

60 

83 

87 

ii 

12                       66 

59 

102 

90 

12 

13                        /6 

57 

123 

93 

13 

14.                      86 

56 

M5 

94 

14 

15 

0-096 

0.54 

0-168 

o-95 

15 

16 

1  06 

53 

193 

96                 16 

17 

116 

Si 

220 

97 

17 

18 

127 

50 

249 

98 

18 

•9 

137 

49 

280 

99 

19 

20 

0-148 

0-47 

0-312 

0-99 

20 

21 

159 

46 

345 

I  -00 

2f 

22 

170 

45 

379 

I-OO 

22 

23 

182 

44 

411 

c-99 

23 

24 

193 

43 

441 

97 

24 

25 

0-205 

0-42 

0-469 

0-96 

25 

26 

216 

41 

495 

93 

26 

27 

228 

40 

521 

91 

27 

28 

270 

39 

545 

89 

28 

29 

253 

38 

568 

86 

29 

30 

0-265 

o-37 

0-590 

0-83 

30 

36 


TECHNICAL  GAS-ANALYSIS 


ture  is  15°.  If  the  temperature  of  the  water  exceeds  15°,  use 
may  be  made  of  the  following  table,  calculated  by  Schloesser 
for  the  expansion  coefficient  of  glass  =  0-000027,  and  the 
values  for  the  expansion  of  water  given  by  the  Physico- 
technical  Reichsaustalt.  The  figures  of  this  table  denote  the 
number  of  cubic  centimetres  which  must  be  subtracted  from 
looo  c.c.  to  give  the  volume  of  water  which  at  f  fills  a  litre 
flask,  calibrated  at  15°,  so  that  it  occupies  a  volume  of  1000  c.c. 
at  15°:— 

TABLE  IV. —  Volumes  of  Water  at  Temperatures  from  15°  to  30°. 


Temperature. 

c.c. 

Temperature. 

c.c. 

I5°C. 

0-000 

23°  C 

1-348 

16 

0-130 

24 

1-563 

17 

0-272 

25 

1.788 

18 

0-42 

26 

2023 

19 

0-58 

27 

2-267 

20 

0.76 

28 

2-520 

21 

o-94 

29 

2-782 

22 

144 

30 

3-053 

The  temperature  of  calibration  should  be  stated  as  in  the 

case  of  liquids,  -%-,  — ,  etc.,  since,  if  the  calibration  has  been 

4      4 

effected  at  15°,  determinations  made  at  this  temperature  and, 
say,  at  25°,  are  not  equivalent. 

The  apparatus  is  placed  in  a  perpendicular  position ;  it  is 
then  filled  up  to  the  top  with  water,  and  this  is  run  off  into  the 
weighing-bottles  in  quantities  of  from  2  to  10  c.c.  according  to 
the  accuracy  desired,  in  such  manner  that  the  outlet  pipe 
constantly  touches  the  wall  of  the  weighing-bottle.  The  water 
is  run  off  quickly  to  a  few  millimetres  above  the  mark ;  one 
must  then  wait  until  the  level  of  the  water  has  become  constant 
and  then  run  it  off  exactly  to  the  mark.  The  running-off  must 
be  performed  by  means  of  glass  jets  attached  to  the  burette 
by  means  of  a  very  short  and  elastic  india-rubber  tube.  The 
outlet-opening  of  the  jet  must  be  as  narrow  as  possible,  because 
this  causes  the  running-out  to  be  slower  and  the  after-running 
to  be  more  quickly  finished  than  in  case  of  a  wider  outlet. 

The  operation  is  repeated  at  least  once,  in  case  of  somewhat 


175  -      9 

200     ,  10 


CALIBRATION  OF  APPARATUS  37 

considerable  deviations  more  frequently,  and  from  the  mean 
observations  a  correction-table  is  calculated,  which  states  the 
real  value  of  the  readings,  reduced  to  the  "  normal "  conditions. 

The  time  interval  of  two  minutes  before  taking  a  reading, 
as  recommended  in  the  case  of  burettes,  is  not  applicable  to 
gas-measuring  tubes,  since  it  depends  on  their  form  and 
diameter.  In  most  cases  the  values  given  below  for  the  time 
taken  by  the  water  used  in  gas-burettes  to  attain  the  final 
position  may  be  taken  as  correct : — 

For  25  c.c.  .        .  3  minutes  For  125  c.c.        .        .      7  minutes 

»     50    „  "  •  "     •  •'  4 

»    75    „  -  •  '•  v  5        „ 

„  100    „  -  .        .'  6        „ 

Before  calibration  the  measuring  apparatus  must  be 
thoroughly  cleansed.  Any  dirt  present  causes  an  irregular 
formation  of  the  meniscus ;  any  traces  of  grease  cause  drops 
of  liquid  to  be  retained  which  influences  the  contents  by  volume. 
The  cleansing  must  be  performed  mechanically  by  means  of 
brushes,  and  chemically  by  means  of  a  hot  soap  solution,  or 
a  mixture  of  potassium  bichromate  and  concentrated  sulphuric 
acid ;  or  in  the  case  of  obstinately  adhering  traces  of  grease,  by 
a  cautious  treatment  with  fuming  nitric  acid,  until  on  rinsing 
with  water,  free  from  any  grease,  this  runs  off  completely 
everywhere.  (Some  operators  use  fluohydric  acid  or  else 
strong  caustic  soda  solution  for  cleansing,  but  neither  of  these 
should  be  employed.) 

When  many  calibrations  have  to  be  made,  the  weighings, 
which  take  a  good  deal  of  time,  may  be  replaced  by  reliable 
normal  measuring  apparatus,  which  certainly  do  not  afford 
the  same  certainty  as  weighings.  The  apparatus  most  usually 
employed  for  this  purpose  is  Ostwald's  pipettes,  Fig.  25.  These 
pipettes  are  made  to  hold  either  2  or  5  c.c.,  according  to  the 
degree  of  accuracy  desired.  They  are  attached  to  the  bottom 
of  the  burette,  as  shown  in  the  figure ;  water  of  exactly 
measured  temperature  is  poured  into  the  burette,  and  by 
opening  the  pinchcock  a  also  enters  into  the  pipette,  exactly 
up  to  the  mark  b.  Now  a  weighing-glass  is  placed  underneath, 
pinchcock  d  is  opened,  and  the  water  run  out  exactly  down  to 
mark  c,  waiting  in  the  end  one,  or  better  two  minutes,  so  as  to 
get  the  last  out-flowing  parts  into  the  weighing-glass.  From  three 


38 


TECHNICAL  GAS-ANALYSIS 


well-agreeing  weighings  of  the  contents  of  the  pipette  between 
marks  b  and  r,  an  average  is  taken  which  holds  good  in  all 
future,  and  from  which  the  contents  of  the  pipette 
are  calculated  for  the  "  true  litre." 

Cushman  (Chem.  News,  1902,  Ixxxv.  p.  77) 
mentions  an  improvement  on  the  Ostwald  pipette 
which  Ostwald  himself  had  previously  adopted.  It 
consists  in  graduating  the  upper  narrow  tube,  care 
being  taken  that  the  capacity  of  the  pipette  from 
the  mark  c  to  about  the  middle  of  the  upper  tube 
b  is  2  c.c.  It  is  then  not  necessary  to  determine 
the  capacity  of  the  pipette  by  a  number  of  accurate 
weighings  as  above,  but  only  to  find  the  value  of 
the  pipette  scale  with  regard  to  the  burette  scale 
by  a  few  determinations.  In  calibrating,  2  c.c.  at 
a  time  are  allowed  to  pass  from  the  burette  into 
the  pipette,  and  the  height  of  the  liquid  in  the 
latter  noted ;  the  corrections  of  the  burette  can 
thus  be  calculated.  This  calibration  is  of  course 
only  relative  ;  if  the  absolute  values  of  the  gradua- 
tions are  required,  the  capacity  of  the  pipette  must 
be  determined  in  the  ordinary  way.  Or  it  may  be 
ascertained  by  a  few  weighings  up  to  which  of  the 
graduations  on  the  upper  tube  the  pipette  has  to 


d 


FIG.  25. 


be  filled  so  that  it  holds  exactly  2  c.c. ;  it  is  subsequently  always 
filled  up  to  this  mark,  and  used  for  correcting  according  to  the 
method  described  above,  whereby  the  corrections  to  be  applied 
to  the  readings  of  the  burette  can  be  found  without  much  cal- 
culation. For  calibrations  according  to  the  true  litre,  attention 
must  be  paid  to  the  details  now  given. 

The  True  Litre. — The  "true  litre"  is  the  volume  which  I  kg. 
of  water  at  4°  occupies  under  standard  pressure.  If  this  space, 
or  divisions  corresponding  to  it,  are  to  be  marked  off  on  a  flask, 
or  burette,  etc.,  the  position  of  the  mark  will  depend  on  the 
temperature  of  the  vessel.  The  standard  temperature  for  this 
purpose  at  the  National  Physical  Laboratory  is  I5°C. ;  that 
means  that  at  a  temperature  of  15°  the  volume  of  the  contents 
of  a  litre  flask  is  the  same  as  that  of  a  kilogram  of  water  at 
a  temperature  of  4°.  The  tables  given  on  pp.  40-41  allow  the 
adjustment  to  be  made  directly  at  any  desired  temperature 


CALIBRATION  OF  APPARATUS  39 

and  pressure,  the  weights  which  must  be  placed  on  the  scale 
pan  to  effect  this  being  given  in  each  case.  They  have  been 
calculated  by  the  German  Normal  Standards  Commission,  and 
communicated  by  Schloesser  (loc.  cit.}. 

Any  two  correct  measuring  apparatus  for  a  litre,  or  any 
subdivisions  of  this,  if  made  of  glass,  and  adjusted  at  different 
temperatures,  differ  only  by  the  difference  in  the  expansion  of 
glass  between  the  two  temperatures,  if  water  of  the  same 
temperature  has  been  used  in  testing  them.  Therefore  it  is 
only  necessary  to  calculate  the  weight  which  is  in  equilibrium 
with  the  weight  of  water  occupying  a  true  litre  measuring 
apparatus  for  the  normal  temperature  =15°.  If  the  temperature 
of  the  air  does  not  greatly  deviate  from  this,  and  the  height  of 
the  barometer  is  not  very  far  from  760  mm.,  sufficiently  correct 
assumptions  may  be  made  for  the  factors  which  influence  the 
buoyancy  of  the  air,  temperature,  pressure,  and  the  degree  of 
moisture ;  and  the  reductions  thus  obtained  may  be  combined 
with  those  due  to  the  temperature  of  the  water.  The  values 
in  Table  V.  A,  p.  40,  can  then  be  employed  directly  in  order  to 
find  how  the  volume  of  a  true  litre  should  be  marked  off  on 
a  flask.  If,  e.g.,  the  air  and  the  water  have  a  temperature  of 
17°,  the  empty  flask  along  with  a  kilogram  weight  is  placed  on 

Ione  scale  pan  and  brought  to  equilibrium  by  a  tare  on  the 
other  pan ;  the  kilogram  weight  is  then  removed,  and  on  the 
same  side  (that  is,  along  with  the  flask)  weights  to  the  amount 
of  2-208  g.  are  placed ;  equilibrium  is  then  re-established  by 
filling  the  flask  with  water  of  17°,  and  the  volume  occupied  by 
this  weight  of  water  marked  on  the  neck  of  the  flask. 

In  the  case  of  greater  deviations  of  the  temperature  of  the 
air  from  15°,  and  of  the  atmospheric  pressure  from  760  mm., 
Table  B,  p.  41,  is  used  to  correct  the  values  of  Table  A.  If,  e.g., 
the  height  of  the  barometer  is  720  mm.,  the  temperature  of  the 
air  25°,  that  of  the  water  24-3°,  the  weight  to  be  added  for 
a  litre  is  : — 

From  Table  A  .  .  .3564  mg. 

B  .  .         -92    „ 

3472  mg. 

The  weight  of  the  volume  of  water  required  to  correspond  to  a 

true  litre  for  the  flask  at  15°  is  therefore  1000  —  3-472  =  966-528  g. 

For    any    other     normal     temperature     (f)     the     amount: 


40 


TECHNICAL  GAS-ANALYSIS 


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CALIBRATION  OF  APPARATUS 


41 


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42 


TECHNICAL  GAS-ANALYSIS 


(/—  15)0-000027  must  be  added  to  the  above  ;  thus  for  a  normal 
temperature  of  20°  all  the  values  of  Table  A  must  be  increased 
by  1000  (20—  15)0-000027=  135  mg.  For  a  water  temperature 
of  20°,  2699+135  =  2834  mg.  must  therefore  be  added. 

If  a  value  differing  from  that  given  in  these  tables  be  chosen 
for  the  mean  expansion  coefficient  of  glass,  then  1000  (af — 
0-00027)  (/— 15°)  must  be  added  to  the  values  of  Table  A,  a 
denoting  the  new  coefficient  of  expansion  of  glass,  and  t  the 
temperature  of  the  water.  The  amount  of  this  correction  is 
always  very  small,  and  is  hardly  likely  to  be  employed  by  the 
chemist  in  calibrating. 

It  is  very  useful  to  construct  for  each  burette  a  table, 
showing  the  true  contents  for  the  cubic  centimetres  read  off. 
Very  conveniently  these  values  are  entered  in  a  system  of 
co-ordinates,  in  which  the  cubic  centimetres  read  off  appear  as 
absciss  values,  the  true  cubic  centimetres  as  ordinate  values. 
By  connecting  the  respective  points,  a  curve  is  obtained,  more 
or  less  deviating  from  a  straight  line ;  this  greatly  facilitates  the 
reduction  of  the  figures  read  off  to  the  true  values. 

In   the   adjustment    of    apparatus,   where    mercury    is    the 

confining  liquid,  which,  as  a  rule, 
in  actual  use  are  placed  inversely 
to  their  position  during  calibration, 
the  meniscus  correction  is  carried 
out  as  follows : — In  the  first  instance 
the  diameter  of  the  vessel  must  be 
ascertained.  In  some  cases,  e.g. 
with  endiometers,  this  can  be  done 
by  direct  mensuration.  Otherwise, 
where  no  special  accuracy  is  required,  only  the  outside 
diameter  is  measured,  and  a  deduction  of  i  mm.  for  smaller, 
or  1-5  mm.  for  larger  widths  is  made  to  compensate  for  the 
thickness  of  the  glass.  The  meniscus  correction  is  then 
calculated  for  the  inside  diameter.  In  doing  this,  the  double 
meniscus  correction  must  be  applied,  since,  as  is  unavoidable  in 
this  case,  the  apparatus  during  actual  use  is  placed  upside  down 
in  comparison  with  its  position  during  the  calibration.  This 
is  made  clear  by  Fig.  26,  a  and  b.  During  calibration  the 
vessel  is  in  the  position  #,  but  in  actual  use  in  the  position  b. 
Suppose  that  in  a  there  is  5  c.c.  mercury  contained  in  the  tube 


5COTL 


FIG.    26. 


MENISCUS  CORRECTIONS 


43 


up  to  the  mark,  there  will  be  in  actual  use,  as  shown  in  b,  twice 

the  difference  between  the  surface  of  the  mercury  and  the  mark. 

The  following  table  indicates  the  double  meniscus  correction 

TABLE  VI. — Double  Meniscus  Correction  for  Mercury  in 
Milligrams. 


Diameter. 

•o. 

•i. 

•2. 

•3. 

•4. 

•5. 

•6. 

•7. 

•8. 

•9. 

mm. 
3 

4 

76 

108 

70 
H3 

82 

118 

85 
123 

88 
129 

91 
135 

94 
141 

97 
148 

IOI 
I56 

104 
I65 

5 

174 

183 

193 

204 

215 

228 

243 

259 

276 

294 

6 

7 
8 

9 

3H 
550 
792 
1038 

336 
574 
817 
1063 

359 

598 
841 
1088 

382 
623 

866 
1113 

406 
647 
890 
1138 

430 
671 
915 
1163 

454 
695 
940 
1188 

478 
719 
964 
1213 

502 

744 
989 
1238 

52* 
768 
1013 
1263 

10 

1288 

1313 

1338 

1364 

1389 

I4H 

1439 

1464 

1490 

1515 

ii 

12 

13 
H 

I54<> 
1796 
2058 
2326 

1566 

1822 
2084 
2353 

I59i 
1848 

2III 
2380 

1617 
1874 
2138 
2407 

1642 
1900 
2165 

2434 

1668 
1926 
2192 
2461 

1694 

1953 
2218 
2488 

1719 
1979 
2245 
2515 

1745 
2005 
2272 
2542 

1770 
2031 
2299 
2569 

IS 

2596 

2624 

2651 

2679 

2706 

2734 

2762 

2789 

2817 

2844 

16 

17 
18 

19 

2872 
3152 
3436 
3724 

2900 
3180 
3465 
3753 

2928 
3209 

3494 
3782 

2956 

3237 
3522 
3812 

2984 
3266 

3551 
3«4i 

3012 
3294 

35*o 
3876 

3040 
3322 
3608 
3899 

3068 
3351 
363? 
3928 

3096 

3379 
3666 

3957 

3124 
3408 

3695 
3987 

20 

4016 

4046 

4076 

4105 

4135 

4165 

4195 

4225 

4254 

4284 

21 
22 
23 
24 

43'4 
4614 
4920 
5230 

4344 
46*5 
495i 
5261 

4374 
4675 
4982 

5293 

4404 
47c6 
5°'3 
5324 

4434 
4736 
5044 
5356 

4464 
4767 
5075 
5387 

4494 
4798 
5106 
5418 

4524 
4828 

5137 
5450 

45C4 
4859 
5168 
548i 

4584 
4889 
5199 

5SU 

25 

5544 

5576 

5608 

5640 

5672 

5704 

5736 

5768 

5800 

5832 

26 

27 

28 

29 

5864 
6185 

6515 
6845 

5896 
6218 
6548 
6879 

5928 
6251 
6581 
6912 

5960 
6284 
6614 
6946 

5992 
6317 
6647 
6979 

6024 
6350 
6680 
7013 

6057 
6383 
6713 
7047 

6089 
6416 
6746 
7081 

6121 
6449 
6779 
7"5 

6153 
6482 
6812 
7148 

30 

7182 

44 


TECHNICAL  GAS-ANALYSIS 


in  milligrams  mercury,  for  tubes  from  3  to  30  mm.  diameter, 
progressing  by  tenths  of  a  millimetre.  It  holds  good  for  all 
practically  occurring  temperatures  of  a  laboratory. 

The  vessel  to  be  calibrated  is  fixed  in  a  stand,  bottom 
upwards,  so  that,  e.g.,  the  top-tap  of  a  gas-burette  is  at  the 
bottom.  The  outlet-tube  of  the  tap  is 
by  means  of  a  strong  india-rubber  pipe 
connected  with  a  funnel,  and  through 
this  at  first  only  so  much  mercury  is  run 
in  that  it  just  fills  up  the  bore  of  the 
tap,  which  is  then  closed,  and  the  elastic 
tube  is  removed.  Any  drops  of  mercury 
adhering  to  the  outlet-tube  are  removed. 
The  apparatus  is  now  placed  on  the 
right-hand  scale  of  a  balance,  or  is 
suspended  from  this,  after  having  placed 
the  balance  on  a  suitable  stand  ;  on  the 
same  scale  weights  are  put  equal  to  the 
weight  of  mercury  corresponding  to  the 
entire  contents  of  the  vessel,  as  indicated 
by  the  table  following  below,  and  the 
equilibrium  is  established  by  placing 
weights  on  the  left-hand  scale.  Now 
the  apparatus  is  again  put  in  the  stand, 
the  india-rubber  pipe  is  attached,  and 
mercury  is  run  in  up  to  the  lowest  mark 
to  be  tested,  care  being  taken  that  the 
meniscus  on  rising  keeps  its  proper 
position.  Then  the  apparatus  is  again 
FIG.  27.  hung  below  the  right-hand  scale  of  the 

balance,  and  weights  are  removed  from  this  until  the  equilibrium 
has  been  re-established. 

Another  way  of  calibrating  burettes,  etc.,  for  use  with 
mercury  is  the  following,  which  is  adapted  to  vessels  provided 
with  a  tap  at  the  top  like  that  shown  at  I.  in  Fig.  27  (taken  from 
Tread  well's  Lehrbuch^  ii.  p.  610).  The  vessel,  after  thorough 
cleaning,  is  placed  in  an  inverted,  perpendicular  position,  as 
shown  at  II.  The  capillary  of  the  tap  is  connected  by  means 
of  a  thick  india-rubber  tube  with  a  mercury  vessel,  tap  a  is 
opened,  and  mercury  is  allowed  to  enter  up  to  a  little  above  the 


CALIBRATION  OF  BURETTES 


45 


top  division.  Now  the  elastic  tube  and  the  mercury  vessel  are 
removed,  and  by  opening  the  tap,  mercury  is  run  out,  until  the 
top  of  the  mercury  meniscus  just  touches  the  horizontal  line  a 
—a  going  through  the  top  line  (which  in  the  proper  position  of 
the  burette  is  the  bottom  mark)  of  the  division.  The  parallax 
fault  is  avoided,  if  the  reading  is  made  by  means  of  a  telescope 
from  a  distance  of  2  or  3  metres.  Now  the  contents  of  the 
tube  are  run  off  into  a  tared  flask,  which  is  weighed  to  I  eg., 
the  temperature  of  the  mercury  is  taken,  and  its  volume  is 
found  from  the  following  table  (drawn  up  by  Schloesser) : — 

TABLE  VII. —  Weights  of  a  Cubic  Centimetre  of  Mercury  at 
Various  Temperatures,  in  Grammes. 


°c. 

•0. 

•l. 

•2. 

•3. 

•4. 

•5. 

•6. 

•7. 

•8. 

•9. 

15 

'3-5593 

13-5591 

I3-55S9 

I3-5587 

'3-5585 

I3-5583 

I3-558I 

13-5579 

'3-5577 

13-5575 

16 

573 

570 

568 

566 

564 

562 

560 

558 

556 

554 

17 

552 

550 

547 

544 

543 

541 

539 

537 

535 

533 

18 

53i 

529 

527 

525 

522 

520 

518 

516 

5H 

512 

19 

Sic 

508 

506 

504 

502 

499 

497 

495 

493 

491 

20 

13.5489 

I3-5487 

I3-5485 

13-54*3 

'3-548i 

13-5479 

I3-5476 

13-5474 

13-5472 

13-5470 

21 

468 

466 

464 

462 

460 

458 

456 

453 

451 

449 

22 

447 

445 

443 

441 

439 

437 

435 

433 

431 

429 

23 

427 

424 

422 

420 

418 

416 

4M 

412 

410 

408 

24 

406 

403 

401 

399 

397 

395 

393 

39i 

389 

387 

25 

'3-5385 

I3-5383 

13-538I 

13-5378 

I3-5376 

'3-5374 

13-5372 

13-5370 

I3-5368 

I3-5366 

26 

364 

362 

360 

358 

355 

353 

35i 

349 

347 

345 

27 

343 

34i 

339 

337 

334 

332 

330 

328 

3^6 

324 

28 

322 

319 

3i8 

316 

SH 

312 

310 

307 

305 

•03 

29 

301 

299 

297 

295 

293 

291 

28c, 

287 

285 

282 

Suppose,  for  instance,  that  the  total  contents  of  the  apparatus 
are  =55  c.c.,  the  normal  temperature  15°,  the  actual  temperature 
of  the  mercury  19-7°.  The  measuring-tube  of  the  apparatus  is 
assumed  to  have  shown  three  different  diameters,  viz.,  7-2,  24-8, 
and  16-5  mm. ;  accordingly  the  meniscus  corrections,  as  shown 
by  Table  III.,  p.  35,  are  598  -548  -3012  mg.  We  want  to 
control  (a)  in  the  narrowest  tube  the  mark  3-0  c.c.,  in  the  central 


46 


TECHNICAL  GAS-ANALYSIS 


part  of  the  apparatus  (b}  the  mark  10  c.c.,  and  in  the  top  part 
(c)  the  mark  50  c.c.  We  conveniently  employ  for  a  tare  the 
weight  of  680  grm.,  equal  to  that  of  50  c.c.  mercury.  The 
weight  of  the  apparatus,  filled  up  to  those  marks,  may  have 
been  39-875  for  a,  272-458  for  £,  677-025  g.  mercury  for  c.  In  the 
position  for  actual  use  these  weights  are  supposed  to  have  been 
increased  by  the  meniscus  corrections,  according  to  Table  VI., 
p.  43,  and  would  therefore  be  40-473  (a) ;  277-939  (b)  ;  680-037  (<:); 
whereas  according  to  Table  VII. on  p.  45,  they  should  have  been 
40-649  (a)  ;  270-990  (b)  ;  677-476  (c).  Hence  those  spaces  contain 
(a)  0-176  g.  too  little;  (b)  6-949  to°  much;  (c)  2-561  too  much, 
which  means  that  the  first  (a)  is  too  little  by  o-oi  c.c.,  the 
second  (b)  too  large  by  0-51,  and  the  third  (c)  too  large  by 
0-19  c.c. 

The  examination  of  apparatus,  adjusted  for  mercury, 
especially  when  they  are  provided  with  a  stopcock,  can  also 
be  performed  by  means  of  water,  employ- 
ing the  tables  worked  out  for  volumetrical 
vessels.  When  doing  this,  the  meniscus 
of  water  during  calibration  is  formed  in 
the  same  position  as  that  of  mercury 
during  actual  use  of  the  apparatus,  as 
shown  in  Fig.  28.  Since  the  meniscus  of 
water  has  a  greater  volume  than  that  of 
mercury,  the  volume  tested  is  found  too 
large  by  the  difference  of  the  simple  meniscus  corrections, 
water  minus  mercury. 

These  differences  are  indicated  in  the  subjoined  Table  VIII., 
in  the  column  ^CM-      If,  for  instance,  in  the  calibration  of  a 

TABLE   VIII. — Differences  of  Simple   Meniscus    Corrections   of 
Water  against  Mercury,  in  Cubic  Centimetres. 


examination  ' 

with  water 

with  mercury 


FIG.  28. 


Diameter. 
mm. 

dCM. 

Diameter, 
mm. 

dCM. 

Diameter, 
mm. 

tfCM 

Diameter, 
mm. 

dCM. 

3 

3 

IO 

20 

17 

104 

24 

247 

4 

6 

II 

27 

18 

123 

25 

264 

5 

8 

12 

36 

19 

H3 

26 

279 

0 

10 

13 

46 

20 

164 

27 

293 

7 

10 

H 

59 

21 

i87 

28 

305 

8 

ii 

15 

72 

22 

208 

29 

315 

9 

15 

16 

88 

23 

220 

30 

424 

GAS-METERS  47 

gas-burette  the  space  marked  20  c.c.  had  been  found  =20-774 
c.c.  when  tested  with  water,  the  gas,  when  employing  mercury 
as  confining  liquid,  would  take  a  space  of  20-774  IGSS  0-261  = 
20-51  c.c. 

Gas-measuring  tubes  with  a  millimeter  scale,  such  as  Bunsen 
employs  for  all  purposes,  may  of  course  be  used  for  all 
temperatures  and  confining  liquids,  but  they  must  be  specially 
calibrated  in  each  case  and  used  with  a  corresponding  table. 
Such  apparatus  is  hardly  ever  employed  in  technical  gas-analysis. 

The  methods  and  conditions  adopted  by  the  English 
National  Physical  Laboratory  for  the  testing  and  calibration 
of  glass  vessels  comprise  chiefly  apparatus  for  the  volumetric 
analysis  of  liquids  and  solids.  We  therefore  refer  to  their 
enumeration  in  Lunge's  Technical  Methods  of  Chemical  Analysis, 
translated  by  C.  A.  Keane,  vol.  i.  part  I  (1908),  pp.  36 
et  seq. 

This  also  holds  good  of  the  rules  laid  down  by  the  Austrian 
Normal-Eichungskommission,  quoted  in  Lunge  and  Berl's 
Chemisch-technische  Untersuchungsmethoden,  vol.  i.  p.  50  (1910) 

The  rules  of  the  United  States  Bureau  of  Standards,  as 
quoted  by  Schloesser  in  Z.  angew.  Chem.  1908,  p.  2168,  do  not 
concern  us,  since  there  apparatus  for  gas-analysis  is  expressly 
excluded  from  standardising. 

MEASURING   IN   GAS-METERS. 

Extremely  important  as  gas-meters  are  for  their  proper 
purpose,  viz.,  measuring  large  quantities  of  coal-gas  and  other 
gases,  they  are  but  rarely  used  in  gas-analysis,  mostly  in  those 
cases  in  which  a  compound,  present  in  minute  proportions, 
has  to  be  estimated  by  absorption.  The  meter  is  then  inter- 
posed between  the  absorbing  vessel  and  an  aspirator,  e.g.  a 
water-jet  pump.  Hence  only  that  portion  of  the  gas  is 
measured  which  is  not  absorbed,  whilst  the  absorbable  portion 
is  mostly  estimated  by  titration  or  gravimetrically. 

Gas-meters  may  also  be  employed  for  finding  the  volume 
of  the  bulk  of  a  gaseous  current  from  which  an  average  sample 
is  to  be  taken. 

We  distinguish  between  wet  and  dry  gas-meters  according 
to  whether  the  gas  is  measured  with  or  without  the  aid  of  a 


TECHNICAL  GAS-ANALYSIS 


confining    liquid.     Only    wet    meters    are    employed    in   gas- 
analysis. 

The  wet  or  hydraulic  gas-meter  (Figs.  29  and  30)  consists 
of  a  cylindrical  sheet-iron  vessel,  resting  horizontally  on  a 
base,  filled  to  a  little  above  half  its  height  with  a  liquid  (water 
or  glycerine  of  sp.  gr.  1-14)  in  which  moves,  round  a 
horizontal  spindle,  a  drum  divided  by  diaphragms  into  several 
chambers  of  exactly  equal  capacity.  There  are  usually  four 
such  chambers,  all  of  them  provided  with  an  opening  near 
the  spindle  for  the  entrance  of  the  gas,  and  an  outlet  opening 


FIG.  29. 


FIG.  30. 


in  the  periphery  of  the  drum,  through  which  the  gas  passes 
into  the  outer  case,  and  thence  into  the  service  pipes.  The 
movement  of  the  drum,  caused  by  the  gas  passing  through, 
is  indicated  by  a  dial  arrangement  so  constructed  that  it 
registers  both  entire  and  fractional  revolutions  of  the  drum. 
Since  the  capacity  of  the  drum  is  known,  the  volume  of  the 
gas  passing  through  can  be  read  off  directly  upon  the  dials. 

The  diagrams  show  a  gas-meter  in  which  the  luting  liquid  is 
filled  in  by  the  plug  d\  the  gas  enters  at  a  and  goes  out 
through  b,  after  having  passed  through  the  drum  in  the 
direction  indicated  by  an  arrow.  A  second  exit  is  provided  by 
the  tap  c,  which  is  used  in  case  the  gas  is  to  be  admitted  to  two 
sets  of  pipes  at  the  same  time. 


GAS-METERS  49 

For  gas-analysis  the  smallest  descriptions  of  meters,  known 
as  "  experimental  gas-meters,"  are  used,  also  at  the  gas-works 
themselves  for  photometrical  purposes.  At  the  Berlin  gas- 
works these  are  36  cm.  high,  and  33  cm.  long ;  they  pass 
a  maximum  of  500  and  a  minimum  of  10  litres  of  gas  per 
hour.  Their  indications  deviate  from  the  truth  in  maximo  by  I 
per  cent,  but  the  actual  error  is  usually  not  above  01  per  cent. 
Such  experimental  gas-meters  are  not  officially  gauged ;  but 
the  makers  do  not  send  them  out  if  they  show  greater  devia- 
tions then  J  per  cent,  on  passing  200  litres  of  gas. 

Specially  constructed  experimental  gas-meters  are  sold,  e.g. 
by  S.  Elster,  Berlin,  by  the  Rotawerke,  Aachen,  etc. 

Where  the  same  kind  of  work,  consisting  in  the  estimation 
of  the  constituent  of  a  gas  occurring  in  minute  quantities — e.g. 
ammonia  in  coal-gas — occurs  frequently,  it  is  preferable  to 
perform  it  always  under  the  same  conditions,  and  therefore  to 
employ  the  same  volume  of  gas  for  every  estimation.  In  such 
cases  the  outlet  of  the  gas  is  regulated  by  means  of  a  tap 
provided  with  a  micrometer  screw.  But  as  the  quantity  of  gas 
to  be  employed  is  usually  large  and  there  is  considerable  time 
required  for  passing  it  through,  it  is  desirable  to  employ  a  gas- 
meter •,  which  is  automatically  stopped  after  a  certain  quantity  of 
gas  has  passed  through.  Automatic  gas-meters  have  been  used 
in  London  for  official  gas-testing  purposes  ever  since  about  the 
year  1872.  Tieftrunk  has  described  such  a  meter  in  which,  each 
time  after  100  litres  of  gas  have  passed  through,  the  index 
uncouples  a  lever,  and  thus  shuts  the  tap  (Verh.  d.  Ver.  2. 
Befordb.  Gewerbfl.,  1876,  5th  Appendix). 

Gas-meters  are  never  altogether  reliable,  but  they  give 
serviceable  approximate  indications,  especially  if  merely  the 
number  of  revolutions  is  noticed,  as  shown  by  the  dials,  without 
regarding  the  absolute  volume  of  the  gas  passed  through. 
Observations  of  this  kind  can  be  made  by  means  of  gas-meters 
with  arbitrarily  divided  dials,  as  used  in  physiological 
laboratories,  and  supplied  by  L.  A.  Riedinger,  of  Augsburg. 
These  meters  pass  up  to  500  or  600  litres  per  hour.  Their  dial 
is  provided  with  two  hands,  one  of  which  (the  smaller)  is  fixed  to 
the  spindle  of  the  drum  and  moves  along  with  it,  indicating  the 
smaller  divisions.  This  hand  makes  100  revolutions  before  the 
second  (larger)  hand  has  completed  one.  The  drum  holds  25 

D 


50  TECHNICAL  GAS-ANALYSIS 

litres,  corresponding  to  one  revolution  of  the  smaller,  or  y^-  of 
a  revolution  of  the  larger  hand.  The  dials  are  arranged  in 
such  manner  that  2  c.c.  can  be  read  off  with  certainty. 

Every  gas-meter  should  be  tested  by  gauging.  This  can  be 
done  by  passing  through  it  varying  quantities  of  air  at  a 
constant  temperature  by  means  of  a  large  aspirator,  provided 
with  a  pressure  gauge,  and  collecting  the  water  running  out  in 
litre-flasks.  The  volume  of  this  water  is  equal  to  that  of  the 
air  employed,  if  the  pressure  gauge  indicates  an  equilibrium 
both  at  the  beginning  and  at  the  end  of  the  experiment. 

Julius  Pintsch,  A.  G.  (Ger.  P.  247871)  describes  a  gas-meter 
intended  for  measuring  gases  under  variable  and  high 
pressures. 

APPARATUS  FOR  MEASURING  THE  VOLUME 
OF  GAS  WHILE  PASSING  THROUGH  TUBES. 

The  "  Rotameter "  of  the  Deutsche  Rotawerke,  Aachen, 
allows  of  directly  reading  off  the  quantity  of  a  gas  (or  liquid) 
passing  through  per  hour.  It  consists  of  a  glass  tube,  wider  in 
the  top  part,  and  provided  with  a  scale  for  litres  per  hour. 
The  gas  entering  from  below  causes  a  float,  provided  with 
steeply  ascending  channels,  to  revolve  quickly  round  its  vertical 
axis,  and  the  position  of  this  float  immediately  indicates  the 
litres  of  gas  passing  through  per  hour.  This  float  revolves  freely 
and  visibly,  without  touching  the  walls  of  the  pipe,  so  that  no 
errors  are  caused  by  friction. 

Ubbelohde  and  Hofsdes  (Z.f.  Elektrochem.,  1913,  xix.  p.  32), 
by  the  name  of  "  Capometer,"  describe  a  contrivance  for  the 
same  purpose,  also  a  viscosimeter  (sold  by  C.  Desaga, 
Heidelberg). 

Nicolardet  (Ann.  Chim.  anal,  appl.,  1913,  p.  136;  Z.  angew. 
Chem.y  1914,  II.  p.  9)  describes  an  apparatus  for  measuring  the 
volume  of  gases  which  are  very  little  soluble  in  water,  and  which 
do  not  act  upon  mercury. 

VARIOUS  APPARATUS  FOR  GAS-ANALYSIS. 

These  apparatus  are  of  two  different  descriptions.  Either 
they  serve  both  for  absorbing  and  measuring  purposes,  or  the 
measuring-tube  is  separated  from  the  absorbing  arrangements. 


WINKLER'S  GAS-BURETTE 


51 


FIG.  31. 


52 


TECHNICAL  GAS-ANALYSIS 


A.  Apparatus/or  absorbing  and  measuring  in  the  Same  Tube. — 
To  this  class  belongs  Bunsen's  classical  eudiometer,  which  we 
do  not  describe  here,  as  it  is  not  used  in  technical  gas-analysis. 
We  also  omit  the  description  of  most  older  apparatus  of  this 
class,  but  we  retain  those  which  are  up  to  the  present  found  in 
very  many  laboratories. 

I.  Winkler' s  Gas-Burette. — This  apparatus,  constructed  in 
1872,  and  shown  in  Fig.  31,  consists  of  two  communicating 
tubes,  the  measuring-tube  A  and  the  level  tube  B,  held  by  the 
clamps  of  an  iron  stand,  and  connected  at  the  bottom  by  an 


A/- 


FIG.  32. 


FIG.  33. 


FIG.  34. 

india-rubber  T-piece  d,  the  free  branch  of  which  is  closed  by  a 
pinchcock.  Tube  A  serves  for  receiving  the  gas,  and  is  at  its 
bottom  provided  with  a  double-bored  side-tap  a,  of  peculiar 
construction.  Its  shape,  as  originally  designed  by  Winkler,  is 
shown  in  Figs.  32  to  34. 

The  tap  possesses  an  axial  bore,  curving  sideways,  and 
issuing  at  right  angles  to  the  others,  an  ordinary  cross  bore. 
Another  kind  of  three-way  tap  has  been  constructed  by  Greiner 
and  Friedrichs,  and  is  shown  in  Figs.  35  to  37.  These,  instead 
of  the  axial  and  cross  bores,  possess  two  slanting  bores ;  they 
are  more  easily  manipulated  and  kept  tight  than  the  former 
construction,  wherefore  I  prefer  them  to  the  original  Winkler 
taps  (sometimes  erroneously  called  Geissler  taps)  for  the  various 


WJNKLER'S  GAS-BURETTE 


53 


apparatus  constructed  by  myself  (cf.  Z.  anal.  Chem.^  1887,  p.  49 
and  Berl.  Ber.y  1888,  xxi.  p.  376). 

The  measuring-tube  A  of  Winkler's  gas-burette,  Fig.  31, 
is  closed  at  the  top  by  a  tap  b.  Between  taps  a  and  b  it 
holds  about  100  c.c.  It  is  exactly  measured  once  for  all,  and 
the  contents  are  marked  on  the  tube.  This  is,  moreover, 
divided  from  the  bottom  upwards  into  tenths  of  a  cubic 
centimetre,  including  the  contracted  pieces  adjoining  the  taps. 
The  lower  one  of  these  contracted  pieces  occupies  about  a 
quarter  of  the  length  of  the  tube,  and  serves  for  measuring 


FIG.  35. 


FIG.  36. 


FIG.  37. 

small  volumes  ;  the  upper  one  should  be  as  short  as  possible, 
so  as  to  prevent  any  liquid  from  adhering  to  it. 

The  level  tube  B  receives  the  absorbing  liquid.  It  is  closed 
at  the  top  by  an  india-rubber  stopper,  through  which  passes 
the  bent  tube  e,  with  an  elastic  tube  attached  to  it.  The  lateral 
outlet-tap  c,  which  increases  the  chance  of  a  fracture,  is  not 
indispensable  and  may  be  left  out. 

The  stand  carries  a  movable  holder  for  the  tubes,  so  that 
these  may  be  placed  at  will  either  in  a  vertical  or  a  horizontal 
position.  The  burette  is  placed  on  a  lead  lined  basin  cy  to 
receive  the  absorbing  liquids  and  rinsings. 

Manipulation. — Open  tap  b,  and  by  means  of  tap  a,  and  of 
an  india-rubber  pump  or  aspirator,  cause  a  current  of  the  gas 


54 


TECHNICAL  GAS-ANALYSIS 


to  be  analysed  to  pass  through  tube  A,  until  all  air  has  been 
driven  out.  According  to  whether  this  is  done  by  pressure  or  by 
aspiration,  either  tap  a  or  tap  b  is  closed  first,  in  order  to  have 


FIG.  38. 

the  gas  under  the  pressure  of  the  outside  atmosphere.  Tap  a 
is  put  in  such  a  position  that  the  inner  end  of  its  longitudinal 
bore  is  turned  outwards. 


WINKLER'S  GAS-BURETTE  55 

The  level  tube  B  is  now  filled  with  the  absorbing  liquid. 
The  air  enclosed  below  tap  a  is  expelled  by  a  momentary 
opening  of  the  pinchcock  attached  to  that  tap.  Thus  the  gas 
and  the  liquid  are  only  separated  by  tap  a.  To  start  the 
absorbing  process,  the  plug  of  a  is  turned  so  as  to  make  a 
connection  between  A  and  B.  The  absorbing  liquid  now 
begins  to  enter  into  A ;  by  blowing  into  the  india-rubber  tube 
attached  to  B,  the  liquid  is  forced  up  a  little  in  A,  and  tap  a 
is  closed  again.  By  alternately  placing  the  tubes  horizontally 
as  shown  in  Fig.  38,  and  vertically,  the  gas  and  the  liquid 
are  brought  into  intimate  contact,  and  the  liquid  quickly 
absorbs  that  portion  of  the  gas  for  which  it  is  intended. 
If,  on  opening  tap  a,  no  more  liquid  enters  into  A,  the 
absorption  is  complete.  We  must  now  cause  the  liquid  to 
assume  the  same  level  in  A  and  B,  either  by  opening  the 
lateral  tap  c  or  by  the  pinchcock  d,  leaving  tap  a  open  in  the 
meanwhile.  The  volume  of  the  liquid  now  contained  in  A  is 
equal  to  that  of  the  gas  absorbed,  and  is  converted  into  per 
cent,  by  volume  by  multiplication  with  100  and  division  by  the 
total  number  of  cubic  centimetres  that  tube  holds. 

After  every  estimation  the  apparatus  is  thoroughly  rinsed 
with  water ;  the  taps  are  dried  with  blotting  paper,  and  the 
plugs  are  again  slightly  greased  all  over.  During  the  time  the 
apparatus  is  out  of  use,  the  plugs  of  the  taps  are  better  taken 
out,  as  they  frequently  stick  very  fast  when  left  in. 

Winkler's  gas-burette  is  principally  applied  for  estimating 
carbon  dioxide  in  gases  from  chimneys,  blast-furnaces,  lime- 
kilns, etc.,  by  means  of  a  moderately  strong  solution  of  caustic 
potash,  and  for  estimating  oxygen  in  atmospheric  air,  etc.,  by 
an  alkaline  solution  of  pyrogallol. 

2.  A.  Lange's  modification  of  the  Winkler  gas-burette  is 
intended  for  the  examination  of  liquid  carbon  dioxide,  or  chlorine, 
and  of  natural  sources  of  gaseous  carbon  dioxide.  It  is  shown 
in  Fig.  39.  Tube  A,  holding  100  c.c.,  is  at  the  top  contracted 
into  a  tube  holding  5  c.c.,  graduated  into  0-05  c.c.  A  is 
connected  by  an  india-rubber  pipe  with  tube  B,  from  the  top 
of  which,  at  c,  descends  an  india-rubber  pipe,  ending  in  a 
glass  tube  which  dips  into  the  250  c.c.  bottle  D,  fixed  on  the 
same  stand.  Caustic  soda  solution  of  sp.  gr.  1-297  is  poured 
into  B,  until  both  B  and  A  are  filled  rather  more  than  half-way 


56 


TECHNICAL  GAS-ANALYSIS 


up.  The  cork,  with  tube  c  and  the  elastic  tube,  is  put  on  B, 
and  by  means  of  another  elastic  tube,  put  on  £,  air  is  blown 

into  A,  until  the  level  of  the 
liquid  is  below  tap  a,  which 
is  then  closed. 

Now  B  is  filled  with  the 
same  solution,  as  well  as  <:, 
the  elastic  tube,  and  D  ;  by 
opening  tap  b  it  is  ascertained 
that  the  bore  of  this  tap  is 
also  filled,  and  the  apparatus 
is  now  ready  for  use.  By 
turning  the  three-way  tap  a 
ninety  degrees,  the  gas  is 
passed  into  A,  until  it  issues 
at  b.  When  b  is  closed  and 
a  opened,  the  potash  solution, 
owing  to  the  absorption  of 
CO2,  will  get  from  D  into  B 
and  A.  After  the  absorption 
has  been  finished,  b  is  opened ; 
the  potash  solution  flows  back 
into  D,  and  the  level  is  auto- 
matically restored  in  the 
tubes,  and  the  apparatus  is 
again  ready  for  use.  Upwards 
of  four  hundred  tests  can  be 
made  without  renewing  the 
potash  solution. 

In  order  to  test  liquid 
carbon  dioxide \  the  iron  bottle 
containing  it  is  placed  in  an 
upright  position  ;  a  coupling- 
piece  is  tightly  screwed  on, 
and  an  elastic  tube  is  drawn 
FIG.  39.  over  its  free  end.  The  valve 

of  the  bottle  is  now  cautiously 

opened  and  is  regulated  so  as  to  yield  a  regular,  moderate  stream 
of  gaseous  carbon  dioxide.  Now  the  elastic  tube  is  slipped 
over  tap  a,  which  is  turned  so  as  to  admit  the  carbon  dioxide 


GAS-BURETTES  57 

into  A ;  the  air  from  this  escapes  through  the  open  tap  b. 
After  one  minute  A  is  filled  with  carbon  dioxide,  and  this 
gas  is  passed  through,  until  needle-shaped  crystals  of  potassium 
hydrocarbonate  appear  in  the  contracted  part  of  A.  Then  b 
is  closed,  the  elastic  tube  is  taken  off,  whereupon  the  pressure 
within  A  becomes  equal  to  that  of  the  outer  air,  and  a  is 
turned  90°,  so  that  A  communicates  with  B.  The  potash 
liquor  at  once  rises  in  A,  and  by  inclining  the  apparatus 
ultimately  to  the  horizontal,  the  absorption  in  A  is  accelerated 
without  the  formation  of  a  vacuum.  The  absorption  is 
completed  by  moving  the  apparatus  upwards  and  downwards ; 
it  is  then  fixed  in  the  vertical  position,  bottle  D  is  lifted  up 
until  the  levels  in  A  and  D  are  in  the  same  plane,  and  the 
volume  of  gas  in  A  is  read  off.  Two  such  tests  should  not 
differ  by  more  than  0-05  per  cent.  As  the  divisions  on  the 
contracted  part  of  A  indicate  0-05  c.c.,  readings  can  be  made 
to  o-oi  c.c. 

In  order  to  take  a  sample  of  the  liquid  carbon  dioxide 
contained  in  an  iron  bottle,  this  is  placed  horizontally  on  a 
stool,  so  that  the  coupling-joint  of  the  valve  points  upwards. 
By  slowly  opening  the  valve,  it  is  generally  possible  to  produce 
a  convenient,  moderate  stream  of  CO2,  but  small  quantities  of 
solid  CO2  are  always  ejected.  In  some  cases  the  adjustment 
of  the  stream  is  very  troublesome  ;  it  issues  in  jerks  and  some- 
times stops,  but  on  touching  the  valve  ever  so  slightly  it 
becomes  so  violent  that  the  elastic  tubes  are  thrown  off.  In 
such  cases  a  reducing- valve  must  be  interposed,  but  the  gas 
must  be  allowed  to  issue  long  enough  to  drive  out  all 
the  air  from  the  valves ;  in  this  case  the  results  agree 
completely  with  those  obtained  directly  from  the  contents  of 
the  bottle. 

In  order  to  examine  liquid  chlorine  and  strong  chlorine  gas •, 
or  the  carbon  dioxide  in  electrolytic  chlorine^  the  process  is 
carried  out  as  just  described ;  but  the  absorbent  employed  is  a 
concentrated  solution  of  ferrous  chloride,  which  absorbs  the 
chlorine  rapidly  and  in  quantity,  leaving  air  and  carbon  dioxide 
behind.  Another  sample  of  the  gas  is  treated  in  a  second 
burette  with  caustic  potash  solution  which  absorbs  the  chlorine 
and  carbon  dioxide,  leaving  only  the  air  as  gaseous  residue. 
The  CO2  is  found  by  the  difference  of  these  two  tests.  It 


58 


TECHNICAL  GAS-ANALYSIS 


would  be  probably  best  first  to  saturate  the  ferrous  chloride 
solution  with  carbon  dioxide. 

3.  Honigmann's  gas-burette,  Fig.  40,  consists  of  a  measuring- 
tube  A,  closed  at  the  top  by  tap  a  \  the  bottom  end  b  is  left  open, 
and  is  connected  with  a  stout  india-rubber  tube.     The  burette 
contains  exactly  100  c.c.  from  a  zero  mark  near  the  bottom  up 

to  the  top ;  it  is  graduated  into  fifth  parts  of  a 
cubic  centimetre.  The  absorbing  liquid  is  con- 
tained in  the  glass  jar  C,  into  which  A  can  be 
plunged  down  to  any  depth. 

This  burette  is  specially  intended  for  esti- 
mating the  percentage  of  carbon  dioxide  in  the 
gases  employed  for  carbonating  the  ammoniacal 
solution  of  sodium  chloride  in  the  ammonia  soda 
process,  but  it  serves  also  for  testing  lime-kiln 
gases  and  other  gaseous  mixtures  containing 
CO2.  The  gas  to  be  tested  is  drawn  through 
A,  until  all  air  has  been  expelled  ;  tap  a  is 
closed,  and  A  is  immersed  in  C,  which  has 
been  previously  filled  with  a  solution  of  caustic 
potash,  exactly  to  the  zero  mark  on  A.  Tap 
a  is  now  opened  for  a  moment,  in  order  to 
equalise  the  pressure  within  and  without,  where- 
upon exactly  100  c.c.  of  gas  is  contained  in  the 
burette.  The  absorption  of  CO2  is  started  by 
immersing  A  a  little  lower,  so  that  its  inside  is 
wetted  by  the  potash  solution,  and  then  putting 
it  out  but  leaving  the  end  of  the  elastic  tube 
within  the  liquid  ;  A  can  thus  be  moved  about  and  downwards. 
The  potash  solution  enters  into  it  as  the  CO2  is  getting  absorbed, 
and  the  absorption  is  soon  completed.  Now  A  is  again  im- 
mersed in  C,  until  the  levels  inside  and  outside  are  the  same, 
and  the  reading  is  taken  which  indicates  directly  the  percentage 
of  CO2  by  volume.  This  apparatus  cannot,  of  course,  yield 
very  accurate  results,  but  its  construction  and  manipulation  are 
very  simple,  and  each  test  takes  only  a  few  minutes.  Both  the 
burette  and  the  elastic  tube  must  be  carefully  rinsed  with  water 
after  each  test. 

4.  The  Bunte  Burette. — This,   one  of  the  most  useful  and 
widely   used    apparatus    for    technical   gas-analysis,   was    first 


FIG.  40. 


BUNTE  BURETTE  59 

described  in  the  J.  Gasbeleucht.,  1877,  p.  447,  and  DingL 
polyt.  /.,  ccxxviii.,  1878,  p.  229.  It  is  an  improvement  of  a 
gas-burette  described  by  Raoult  in  Comptes  rend.,  Ixxxii.  p.  844 
(1876).  It  is  shown  in  Fig.  41. 

The  measuring-tube  A  is  at  the  top  closed  by  a  three-way 
glass  tap  a,  preferably  of  the  Greiner-Friedrichs  shape  (supra, 
p.  52),  surmounted  by  a  funnel  t,  and  at  the  bottom  closed  by  the 
plain  glass  tap  b.  The  space  between  taps  a  and  b  is  rather  more 
than  noc.c.,  and  is  divided  into  fifths  of  a  cubic  centimetre. 
The  mark  100  coincides  with  the  capillary  of  the  upper  tap  a 
(this  capillary  remains  filled  with  water  and  is  therefore  not 
included) ;  the  zero  mark  is  6  or  8  c.c.  above  the  tap  b,  and 
the  division  is  carried  10  c.c.  below  this.  The  gas  in  this 
burette  is  always  measured  at  the  atmospheric  pressure,  plus 
the  pressure  of  the  column  of  water  contained  in  the  funnel  t 
up  to  the  mark.  The  burette  was  formerly  provided  with  a 
glass  jacket  to  prevent  cooling,  but  this  was  left  off  later  on  as 
being  unnecessary  in  an  ordinary  laboratory. 

This  tube  is  fixed  to  an  iron  stand  by  means  of  an  easily 
opened  clamp.  A  second  arm  on  this  stand  carries  the  funnel 
B,  which  can  be  connected  by  an  india-rubber  tube,  about  3 
mm.  wide,  with  the  capillary  bottom  end  of  the  burette. 

To  the  apparatus  belong  further  a  small  glass  or  porcelain 
cup  C  for  holding  the  absorbing  liquids,  and  two  aspirating 
bottles,  D  and  E,  of  the  shape  shown  in  the  diagram.  Bottle  D 
serves  for  forcing  water  into  the  burette,  or  withdrawing  it  there- 
from. In  both  cases  the  rubber  end  n  is  put  upon  the  bottom 
capillary  b  ;  and  air  is  during  this  operation  blown  by  the  mouth 
into  the  tube  ;//,  so  that,  during  the  fixing  of  the  tube  on  by 
water  is  always  running  out  of  «,  and  no  air-bubble  can  get  in. 
This  precaution  must  never  be  omitted.  If  larger  quantities  of 
liquid  are  to  be  withdrawn  from  the  burette,  the  bottle  E  is 
employed  ;  it  is  attached  directly  to  the  burette,  the  air  having 
been  evacuated  from  it  by  means  of  a  water-jet  pump. 

By  permission  of  Professor  Bunte,  we  take  the  following 
points  from  his  instructions  "  Zum  Gaskursus,"  printed  in  1906 
"as  manuscript"  for  the  use  of  his  students  in  gas-analysis. 

Bunte  burettes,  in  order  to  properly  fulfil  their  purpose, 
must  answer  to  the  following  conditions  : — The  capillary  below 
the  bottom  tap  b  must  not  allow  any  water  to  flow  out,  even  on 


60 


TECHNICAL  GAS-ANALYSIS 


FIG.  41. 


BUNTE  BURETTE  61 

shaking  the  burette.  The  three-way  tap  at  the  top  (a)  must  be 
so  constructed  that  all  its  three  bores  can  be  closed  (this  is 
quite  easy  in  the  case  of  Greiner-Friedrichs  taps).  The  taps 
must  be  greased  with  a  fused  mixture  of  2  parts  Para-caoutchouc, 
2  parts  beeswax,  and  10  parts  tallow,  or  a  mixture  of  vaseline 
and  Para-caoutchouc.  They  must  close  perfectly  tightly  even 
against  a  strong  vacuum.  The  confining  water  must  have 
exactly  the  same  temperature  as  the  working-room,  and  this 
must  remain  perfectly  constant  during  the  analysis.  The 
burette  must  be  touched  for  handling  only  at  the  top  funnel  (/) 
or  at  the  capillary  branches.  The  marking  is  to  be  controlled 
by  running  out  the  water  from  2  to  10  c.c.  (vide  supra,  pp.  36, 
et  seq.).  After  the  absorption  of  a  gas,  first  water  is  allowed  to 
enter  from  below,  and  then  the  working  pressure  is  established 
by  allowing  water  to  run  down  from  the  upper  funnel  (f) ;  this 
funnel  is  filled  up  to  the  mark,  the  upper  tap  (a)  is  opened, 
waiting  for  one  minute  until  the  surface  of  the  water  in  the 
burette  does  not  rise  any  more. 

The  gas  to  be  tested  is  introduced  into  the  burette  either 
when  this  is  empty  (the  funnel  t  being  full)  by  passing  the 
gas  through  until  all  the  air  has  been  driven  out,  then  shutting 
first  the  bottom  tap  b  and  immediately  afterwards  the  top 
tap  a ;  or  else  after  filling  the  burette  with  water,  by  opening 
both  taps,  until  the  water  has  sunk  about  I  c.c.  below  the  zero 
mark,  and  then  closing  first  the  upper,  after  this  the  lower  tap. 
If  the  gas  to  be  sampled  is  under  low  pressure,  a  sample  of  it 
must  be  taken  by  means  of  an  india-rubber  pump,  or  an 
aspirating  bottle,  or  a  water -jet  pump,  connected  with  the 
bottom  capillary. 

It  is  hardly  necessary  to  say  that  before  introducing  a  fresh 
sample  of  gas  into  the  burette,  this  must  be  most  thoroughly 
cleaned.  If,  e.g.,  it  is  merely  employed  for  estimating  carbon 
dioxide,  and  any  alkaline  liquid  were  left  adhering  to  the  glass 
before  introducing  the  new  gas-sample  (a  fault  not  infrequently 
committed  in  works'  laboratories),  too  little  CO2  would  be 
found  in  the  fresh  sample,  because  some  of  it  would  be  taken 
out  by  the  adhering  liquid  before  measuring  the  gas. 

The  ordinary  manipulation  is  as  follows : — Water  is  run 
into  the  burette  through  the  funnel  B,  until  it  begins  to  enter 
into  the  top  funnel  t.  The  taps  are  now  closed,  and  the  india- 


62  TECHNICAL  GAS-ANALYSIS 

rubber  tube  is  detached  from  the  bottom  of  the  burette.  The 
three-way  tap  a  is  now  turned  so  that  the  burette  communicates 
with  the  tube  conveying  the  gas,  which  tube  is  already  rilled 
with  the  same,  and  the  gas  is  drawn  into  the  burette  by 
running  water  out  of  the  bottom  tap  b.  Rather  more  than 
100  c.c.,  say  100-5  c-c>  °f  gas  1S  allowed  to  enter  the  burette, 
tap  b  is  turned  so  that  all  its  openings  are  closed,  and  the 
exact  adjustment  to  the  zero  mark  is  made  as  follows : — By 
means  of  the  bottle  D  sufficient  water  is  forced  into  the  burette 
to  compress  the  gas  to  about  95  c.c. ;  then  b  is  closed,  the  bottle 
D  is  taken  off,  and  by  cautiously  turning  the  tap  b  the  water  is 
run  out  again,  exactly  to  the  zero  mark.  The  gas  is  still  under 
a  plus  pressure,  and  now,  by  a  last  operation,  that  pressure  has 
to  be  established  at  which  every  reading  has  to  take  place. 
For  this  purpose  the  funnel  /  is  filled  with  water  up  to  the 
mark,  and  tap  a  is  opened  for  an  instant,  which  causes  the 
excess  of  gas  to  escape  through  the  water  in  /.  The  burette 
ought  now  to  contain  exactly  100  c.c.  of  gas  at  the  pressure 
of  the  atmosphere,  plus  the  pressure  of  the  column  of  water 
standing  in  the  funnel  t.  If  the  water  is  not  exactly  at  the 
zero  mark,  its  level  is  read  off  and  the  calculations  made  on  the 
real  volume  of  the  gas. 

Now  a  little  water  fs  run  out  of  the  funnel  /  by  means  of 
the  three-way  tap  a,  into  a  short  bit  of  india-rubber  tube,  which 
is  then  closed  by  a  glass  rod  ;  this  remains  as  long  as  the  tap 
is  not  used. 

The  absorbing  liquids  are  introduced  in  the  following  way  : — 
The  water  contained  in  the  burette  is  drawn  off  by  means  of 
the  bottle  D  down  to  the  tap  b,  which  is  held  fast  and  is 
immediately  closed  as  soon  as  the  water  has  gone  down  to  the 
capillary  part.  The  end  of  the  burette  is  now  dipped  into  the 
cup  C,  which  has  been  charged  with  the  absorbing  liquid.  If 
tap  b  is  now  opened,  a  volume  of  the  absorbing  liquid,  almost 
equal  to  that  of  the  water  drawn  off,  enters  the  burette  and 
rises  in  it  almost  up  to  the  zero  point,  but  not  quite,  owing  to 
its  higher  specific  gravity.  In  any  case  the  quantity  of  liquid 
thus  introduced  suffices  for  removing  the  absorbable  constituent 
of  the  gas,  and  in  order  to  effect  this  it  is  only  necessary  to 
bring  the  gas  and  the  liquid  into  intimate  contact.  For  this 
purpose  the  burette,  after  closing  the  tap  b,  is  taken  hold  of  by 


BUNTE  BURETTE  63 

the  upper  capillary  between  the  first  finger  and  the  thumb, 
closing  the  funnel  top  by  the  hand,  and  the  burette  is  moved 
up  and  down  in  short,  but  not  violent  jerks.  When  the 
absorption  is  complete,  the  bottom  end  of  the  burette  is  again 
dipped  into  the  cup  C,  and  tap  b  is  opened,  whereupon  liquid 
enters  in  the  place  of  the  absorbed  gas.  If,  on  repeating  the 
just-described  operations  the  liquid  within  the  burette  remains 
at  the  same  level,  the  reading  may  be  taken.  First,  however, 
the  gas  has  to  be  put  under  the  proper  pressure  by  running 
water  into  the  burette  out  of  the  funnel  t  (whereby  also  the 
inside  of  the  burette  is  rinsed)  and  filling  t  with  water  up  to 
the  mark. 

Since  the  adhesion  of  the  absorbing  liquids  differs  from  that 
of  water,  it  is  preferable  to  remove  those  liquids  by  water  and 
to  repeat  the  reading.  For  this  purpose  both  taps  a  and  b 
are  opened,  water  being  run  into  funnel  t  in  a  steady  stream, 
and  thus  the  burette  is  rinsed  until  the  liquid  running  out  is 
pure  water.  No  gas  is  lost  in  this  way,  and  therefore  after 
the  water  contained  in  the  burette  has  been  drawn  off  in  the 
above-described  way,  a  different  reagent  can  be  introduced 
in  order  to  absorb  another  of  the  gaseous  constituents.  In  the 
same  way  a  third  and  fourth  gaseous  constituent  can  be 
removed,  and  its  volume  determined  by  rinsing  out  and  intro- 
ducing suitable  absorbents.  But  as  this  manipulation  requires 
the  use  of  a  large  quantity  of  water,  by  which  some  of  the  gas 
may  be  dissolved,  it  is  preferable  to  draw  off  most  of  the 
absorbing  liquid  by  suction  and  wash  the  burette  by  means  of 
a  few  cubic  centimetres  of  water,  which  is  again  sucked  off, 
repeating  this  as  often  as  may  be  necessary. 

We  shall  further  illustrate  the  manipulation  of  the  Bunte 
burette  by  describing  a  determination  of  carbon  dioxide  say  in 
coal-gas.  For  this  I  c.c.  of  caustic  potash  solution  is  introduced 
in  the  way  described  on  p.  62.  After  closing  tap  £,  the  burette 
is  taken  out  of  the  clamp,  taking  hold  of  it  with  the  thumb  and 
first  finger  of  the  right  hand  at  the  capillary  below  the  upper 
tap  #,  and  it  is  inclined  in  such  manner  that  the  whole  of  its 
inside  gets  wetted  by  the  caustic  liquor,  or  else  jerked  as 
described  supra.  The  absorption  of  the  CO2  is  almost  instan- 
taneous. The  burette  is  put  back  into  the  clamp,  the  liquor  is 
allowed  a  minute  or  so  to  run  down,  water  is  again  poured  into 


64  TECHNICAL  GAS-ANALYSIS 

the  top  funnel  /,  and  by  suitably  turning  tap  a,  about  i  c.c.  of 
water  is  run  into  the  burette,  whereby  the  caustic  liquor  is 
washed  off  the  glass.  The  liquor  at  the  bottom  is  drawn  out 
by  means  of  the  aspirating  bottle  D,  and  the  washing  of  the 
burette  is  repeated  with  I  or  2  c.c.  of  water.  The  volume  of 
gas  left  in  the  burette  must  now  be  read  off.  For  this  purpose 
water  is  introduced  by  means  of  funnel  B,  the  elastic  tube  of 
which  is  put  on  the  bottom  outlet  with  the  above-described 
precautions  against  any  air  getting  in.  When  no  more  water 
enters  into  the  burette  tap  b  is  closed.  The  gas  in  A  is  now 
under  plus  -  pressure.  The  elastic  tube  is  taken  away,  and 
water  is  run  out  of  tap  b  as  much  as  will  do  so  of  its  own 
accord.  The  gas  is  now  under  minus-pressure.  If,  therefore, 
tap  a  is  opened  so  that  A  communicates  with  funnel  /,  some 
water  runs  out  of  this  into  A,  and  is  replaced  by  other  water  up 
to  mark  on  t,  whereby  the  gas  now  contained  in  the  burette  is 
under  the  same  conditions  of  pressure  as  on  measuring  off  the 
original  gas.  After  closing  tap  a,  a  minute  is  allowed  for  the 
water  to  run  off  the  inside  surface  of  A,  and  the  volume  in  A  is 
read  off. 

The  Bunte  burette  can  be  employed  for  most  gas-analytical 
operations,  either  by  itself  or  in  connection  with  other  apparatus. 
Some  of  its  principal  applications  are  : — 

1st.  For  the  estimation  of  carbon  dioxide  in  mixtures  of 
that  gas  with  air,  or  fire-gases,  gases  from  blast-furnaces,  lime- 
kilns, gas-producers,  and  so  forth,  by  means  of  potassium  hydrate 
solution. 

2nd.  For  the  estimation  of  oxygen,  either  by  itself  (as  in 
atmospheric  air)  or  when  mixed  with  carbon  dioxide,  nitrogen, 
and  other  gases.  If  CO2  is  present  this  is  in  any  case  taken 
out  by  potash  solution,  and  the  oxygen  afterwards  absorbed  by 
a  strongly  alkaline  solution  of  pyrogallol. 

yd.  For  the  estimation  of  carbon  monoxide  by  means  of 
absorption  in  a  solution  of  cuprous  chloride  in  hydrochloric 
acid.  Before  doing  so  any  carbon  dioxide  and  oxygen  must  be 
taken  out  first,  whether  they  are  to  be  estimated  or  not. 

4//z.  For  the  estimation  of  hydrocarbons,  of  hydrogen,  of 
methane,  etc.,  as  will  be  described  later  on  in  connection  with 
the  analysis  of  coal-gas. 

For  some  of  these   purposes   the  Bunte  burette  must  be 


ABSORBING  APPARATUS  65 

combined  with  apparatus  for  fractional  combustion,  or  provided 
with  platinum  points  for  producing  an  explosion  by  means  of 
the  electric  spark.  These  arrangements  will  be  described  later 
on  when  treating  of  the  methods  in  question. 

Various  modifications  of  the  Bunte  burette  have  been 
proposed — e.g.  by  Francke,  Schuhmacher,  Pfeiffer — but  these 
need  not  be  described  in  this  place.  A  modification,  particularly 
arranged  for  working  with  sulphuretted  hydrogen,  is  described 
in  the  49^/2  Report  of  the  Alkali  Inspectors  for  the  year  1912, 
pp.  20  et  seq. 

^.—APPARATUS  PROVIDED  WITH  ABSORBING 
PARTS  SEPARATED  FROM  THE  MEASURING- 
TUBE. 

The  just-described  Bunte  burette  in  some  of  its  applications 
belongs  already  to  this  class,  as  is  made  clear  in  describing 
it.  In  this  kind  of  apparatus  the  absorption  of  a  gaseous 
constituent  is  not  carried  out  in  the  measuring-tube  itself,  but 
in  a  separate  vessel  which  serves  for  holding  the  absorbing 
liquid,  and  for  bringing  the  gas  into  contact  with  it  after  being 
measured.  When  the  absorption  has  been  finished,  the 
remaining  gas  is  again  transferred  to  the  measuring-tube  where 
its  volume  is  read  off.  The  volume  of  the  gas  taken  out  by 
the  absorbing  reagent  follows  from  the  difference  of  the  two 
readings. 

This  way  of  proceeding  admits  of  thoroughly  utilising  the 
absorbent,  and  dispenses  with  washing  out  the  measuring-tube 
after  each  estimation.  In  this  way  hundreds  of  measurings 
can  be  carried  out  without  necessitating  any  intermediate 
operation,  and  before  changing  and  refilling  the  apparatus. 
Hence  such  apparatus  are  eminently  adapted  for  technical 
purposes,  especially  for  the  regular  control  of  technical 
operations. 

The  measuring  and  absorbing  vessels  must  be  capable  of 
being  connected  with  each  other  either  in  a  temporary  or  a 
permanent  way.  The  connection  is  usually  made  by  a  narrow 
capillary  tube  whose  contents  scarcely  amount  to  o-i  c.c.  ; 
hence  the  quantity  of  air  contained  in  it,  which  gets  mixed 
with  the  gas  to  be  examined,  is  so  slight  that  it  does  not 

E 


66  TECHNICAL  GAS-ANALYSIS 

sensibly  influence  the  result.  In  special  cases  this  capillary 
tube  may  be  filled  with  water  in  order  to  avoid  that  slight 
admixture  with  air. 

The  first  apparatus  of  this  class  was  that  constructed  by 
Scheibler  for  estimating  the  carbon  dioxide  in  the  saturation 
gases  of  sugar  works.  This  apparatus,  like  some  others,  did 
very  good  service  in  its  time,  but  has  been  superseded  by 
others  of  a  simpler  or  more  efficient  description,  which  we 
shall  now  enumerate. 

ORSAT'S   APPARATUS. 

The  apparatus  now  generally  known  by  this  name  and 
used  in  thousands  of  factories  has  not  been  first  proposed  by 
Orsat,  but  by  Regnault  and  Reiset,  in  1853,  for  scientific 
purposes.  Its  first  application  for  technical  purposes  is  due 
to  Schlosing  and  Rolland,  in  1868  (Ann.  Chim.  Phys.  (iv.)  xiv. 
p.  55),  who  gave  it  already  the  form  now  generally  used;  it 
was  improved  by  Orsat  in  1875  (Ann.  des  Mines  (vii.)  viii. 
pp.  485,  501),  and  later  on  by  Salleron,  Aron,  Ferd.  Fischer, 
Muencke,  Lunge,  and  various  others. 

We  show  in  Fig.  42  the  "  Orsat "  as  modified  by  F.  Fischer. 
The  measuring-tube  or  burette  A  contains  exactly  100  c.c.  from 
the  zero  mark  near  its  bottom  to  the  capillary  end  at  the  top. 
The  narrower  portion  of  the  measuring-tube  is  divided  into  tenths 
of  a  cubic  centimetre.  The  burette  A  is  surrounded  by  a  water- 
jacket,  in  order  to  protect  it  against  the  influence  of  changes 
of  the  outer  temperature  during  the  operation.  This  water- 
jacket  is  closed  at  top  and  bottom  by  india-rubber  stoppers, 
and  is  sometimes  provided  with  a  white  background  of  opaque 
glass,  on  which  the  black  divisions  of  the  burette  are  more 
plainly  visible.  The  burette  ends  at  top  and  bottom  in  thick 
capillary  tubes  which  fit  into  suitable  projections  of  the  wooden 
frame.  The  bottom  end  is  connected  by  an  india-rubber  tube 
with  a  pressure  bottle  L,  filled  two-thirds  with  water;  the 
top  is  connected  with  a  glass  capillary,  bent  at  a  right  angle 
and  ending  in  the  three-way  cock  c,  which  allows  of  connection 
with  the  gas  supply  and  the  tube  B,  or  between  B  and  A,  or 
between  A  and  the  outside  air.  The  horizontal  capillary  is 
provided  with  two  capillary  branches,  which  are  continued  into 


ORSAT  APPARATUS 


67 


glass  taps  n  and  m,  with  a  mark  on  each  of  them  below  the 
tap,  which  at  their  capillary  bottom  ends  are  connected  by 
india-rubber  joints  with  the  U-shaped  absorption  vessels, 
D  and  E,  usually  called  "pipettes."  The  horizontal  capillary 
tube  is  at  its  end  bent  down  and  connected  with  a  U-tube  B, 
filled  with  cotton-wool,  in  order  to  retain  all  soot  and  dust 
contained  in  the  gas  sample. 


FIG.  42. 

The  "  pipettes "  D  and  E  are  filled  with  bundles  of  glass 
tubes,  so  as  to  provide  a  large  surface  of  contact  between  the 
gas  and  the  absorbent ;  the  open  end  of  each  pipette  is  closed 
by  a  rubber  stopper  to  which  a  thin  rubber  ball  is  attached,  the 
object  of  which  is  to  protect  the  contained  liquids  from  contact 
with  the  air. 

The  mark  in  the  capillary  end  of  the  glass  taps  n  and  m 


68  TECHNICAL  GAS-ANALYSIS 

being  above  the  joint  with  the  pipettes,  this  joint   is  always 
wetted  inside  by  water  and  is  therefore  easily  kept  tight. 

Since  these  glass  taps  sometimes  stick  fast  and  are  then 
easily  broken  in  trying  to  open  them  (this  ought  not 
to  happen  if  they  are  properly  greased  with  vaseline  or  other 
suitable  substances,  as  is  anyhow  necessary,  cf.  p.  15),  Naef 
recommends  in  lieu  of  them  the  so-called  Bunsen  valves,  z.£., 
india-rubber  tubes  with  a  glass  ball  inside  (Chem.  Ind.,  1885, 
p.  289).  Olschewsky  employs  india-rubber  tubes  with  ordinary 
pinchcocks. 

To  prepare  the  apparatus  for  use,  the  pressure  bottle  L  is 
filled  with  water  and  then  raised  so  as  to  drive  out  the  air  in 
the  burette  A  through  the  tap  c.  The  pipette  D  is  then  filled, 
say,  with  potassium  hydroxide  solution  for  the  absorption  of 
carbon  dioxide,  and  the  pipette  E  with  pyrogallol  solution  for 
the  absorption  of  oxygen.  If  carbon  monoxide  is  to  be 
estimated  as  well,  the  apparatus  is  provided  with  a  third 
capillary  branch  glass  tap  and  a  special  absorbing  pipette,  the 
glass  tubes  of  which  contain  copper  spirals,  in  order  to  protect 
the  ammoniacal  cuprous  chloride  solution  with  which  this 
pipette  is  filled  against  oxidation. 

The  method  of  preparing  the  absorbing  solutions  will  be 
described  later  on. 

To  introduce  the  absorbing  liquids,  they  are  poured  into  the 
respective  pipette  from  the  back,  after  taking  off  its  stopper  so 
as  to  fill  about  half  of  it,  and  then  drawn  up  to  the  mark  in  or  n 
by  opening  the  tap  of  that  pipette  and  lowering  the  pressure 
bottle  L ;  when  the  liquid  reaches  the  mark,  the  tap  is  closed 
and  the  rubber  ball  inserted  at  the  back  of  the  pipette. 

Before  proceeding  with  an  analysis,  the  apparatus  should 
first  be  tested  to  see  whether  it  is  air-tight.  This  is  done  by 
filling  the  burette  A  with  water,  then  closing  the  tap  c,  and 
lowering  the  pressure  bottle  L,  when  it  will  at  once  be  seen 
from  any  change  in  level  of  the  water  in  A,  whether  there  is 
any  leakage. 

In  order  to  introduce  the  sample  of  gas,  A  is  again  filled 
with  water,  the  tap  c  turned  so  as  to  communicate  with  B  and 
the  outside  air  and  the  rubber  aspirator  C,  which  is  connected 
with  the  gas  supply,  and  then  attached  to  the  exit-tube  of  B. 
After  clearing  out  the  air  in  B  by  aspirating,  the  tap  c  is  turned 


ORSAT  APPARATUS  69 

so  as  to  connect  the  gas  supply  with  the  burette  A,  and  the 
sample  introduced  by  lowering  the  pressure  bottle  L.  A  little 
more  than  100  c.c.  is  syphoned  into  A,  and  the  tap  c  is  then 
closed.  To  obtain  exactly  100  c.c.  for  analysis,  the  gas  is 
compressed  to  the  zero  mark  by  raising  L ;  the  rubber  tube  s 
between  L  and  A  is  then  closed  either  by  the  pinchcock  or  by 
the  fingers,  and  the  tap  c  momentarily  opened  to  the  outside 
air,  so  as  to  establish  the  atmospheric  pressure  on  the 
contained  gas. 

Before  introducing  the  gas  into  A,  care  must  be  taken  to 
completely  remove  the  air  contained  in  the  tubes  connected 
with  the  chimney,  gas-flue,  or  other  place  whence  the  gas  is  to 
be  taken.  This  is  done  by  turning  tap  c  so  as  to  connect  the 
rubber  aspirator  C  with  the  source  of  the  gas,  and  compressing 
and  loosening  C  ten  or  twelve  times,  whereupon  the  connecting 
tube  is  sure  to  be  filled  with  the  gas  to  be  examined. 

Suppose  we  want  now  to  determine  the  carbon  dioxide. 
We  open  the  tap  m  and  transfer  the  gas  from  the  burette  A 
into  the  pipette  D,  by  raising  the  pressure  bottle  L  with  the 
left  hand,  so  that,  on  opening  the  pinchcock  s  by  the  right 
hand,  gas  enters  into  D.  Now  L  is  again  lowered,  until  the 
caustic  liquor  in  D  rises  about  to  the  rubber  junction  below 
m,  and  the  gas  is  once  more  driven  into  D  by  raising  L. 

This  operation  is  repeated  several  times,  by  alternately 
lowering  and  raising  L,  until  the  absorption  is  complete. 
Finally,  the  level  of  the  liquid  in  D  is  brought  up  to  the  mark 
mt  the  attached  tap  closed  and  the  reading  in  the  burette 
taken,  the  pressure  of  the  gas  in  A  being  adjusted  to  that  of 
the  atmosphere  by  raising  L,  so  that  the  height  of  the  liquid 
in  L  and  that  in  the  burette  is  the  same.  The  reading  obtained 
gives  the  percentage  of  CO2  directly. 

Precisely  in  the  same  way  the  gas  is  now  two  or  three 
times  passed  into  the  pyrogallol  pipette  E  until  no  further 
absorption  takes  place,  and  the  remaining  gas  again  transferred 
into  A.  The  diminution  of  the  volume  of  gas  against  the  last 
reading  indicates  the  percentage  of  oxygen. 

If,  as  is  a  very  usual  case,  any  carbon  monoxide  present  in 
the  sample  is  to  be  determined,  the  apparatus  is  for  this 
purpose  provided  with  a  third  pipette,  charged  with  an 
ammoniacal  solution  of  cuprous  chloride,  as  mentioned  supra^ 


70  TECHNICAL  GAS-ANALYSIS 

p.  64.  The  preparation  of  this  solution  will  be  described 
later  on.  As  it  becomes  unreliable  after  some  time,  Fischer 
prefers  to  omit  this  determination  in  the  analysis  of  furnace- 
gases,  but  in  that  of  producer-gases  and  similar  cases  the 
carbon  monoxide  is  just  one  of  the  principal  constituents  of 
the  gas,  and  must  be  determined  in  one  way  or  another. 

When  the  analysis  is  completed,  the  residual  gas  is  cleared 
out  of  the  burette  A,  and  the  apparatus  is  again  ready  for  use. 
The  estimation  of  CO2  and  O  can  be  completed  in  five  minutes, 
with  an  accuracy  of  0-2  per  cent.  The  estimation  of  CO  takes 
rather  more  time,  as  we  shall  see  later  on. 

When  the  absorption  after  prolonged  use  of  the  apparatus 
is  becoming  too  slow,  the  contents  of  the  pipettes  getting 
exhausted,  they  are  removed  by  means  of  a  small  syphon,  and 
the  pipettes  are  thoroughly  washed  out  with  distilled  water 
before  introducing  a  fresh  charge  of  the  absorbent.  In  case 
any  of  the  absorbing  liquid  should  have  got  into  the  capillary 
tube  above  the  stopcocks  of  the  pipettes,  the  tubes  should 
be  thoroughly  washed  out  with  water  through  the  tap  c,  the 
other  taps  being  shut,  and  the  water  in  A  and  L  renewed.  It 
is  important  to  grease  all  the  stopcocks  before  the  apparatus 
is  put  aside  after  use. 

In  order  to  save  the  trouble  of  repeatedly  transferring  the 
gas  from  the  burette  into  the  absorbing  pipettes  and  back, 
several  automatically  acting  apparatus  have  been  constructed, 
e.g.y  by  Namias  {Stahl  u.  Eisen,  1896,  p.  788);  Le  Docte  (Chem. 
Zeit.,  1900,  p.  375);  Cario  (Ger.  P.  98667;  Chem.  Zeit., 
1898,  p.  977). 

L.  Kaufmann  &  Co.  (Chem.  Zeit.  Rep.,  1901,  p.  26) 
describe,  by  the  name  of"  Ados,"  an  apparatus  for  automatically 
analysing  furnace  gases  and  continually  registering  the  results. 
L.  M.  Dennis  (Gas-Analysis^  1913,  pp.  85  et  seq)  describes  an 
improved  form  of  the  Orsat  apparatus. 

The  absorbing  solutions  usually  employed  are  the 
following : — 

1.  For  absorbing  carbon  dioxide :  a  solution  of  potassium 
hydroxide  of  sp.  gr.   1-25.     Caustic  soda  solutions   are  not  to 
be    recommended,  as  they  act    more  strongly  upon  the  glass, 
and  as  the  sodium  carbonate  formed  crystallises  out. 

2.  For  absorbing  oxygen  :     the  same  solution  of  potassium 


ORSAT-LUNGE  APPARATUS  71 

hydroxide  in  which  15  to  25  g.  of  pyrogallol  are  dissolved 
for  each  apparatus. 

In  lieu  of  this  reagent,  some  prefer  very  thin  sticks  of 
phosphorus,  the  pipette  being  filled  up  with  water,  but 
containing  no  glass  tubes. 

3.  For  absorbing  carbon  monoxide  :  an  ammoniacal  solution 
of  cuprous  chloride,  the  preparation  of  which  will  be  described 
in  the  special  chapter  on  Absorbents. 

The  principal  applications  of  the  ordinary  Orsat  apparatus, 
with  two  or  three  absorbing  pipettes,  are :  for  controlling  the 
efficiency  of  furnace  fires  by  estimating  the  carbon  dioxide  in 
the  chimney-gases  ;  for  estimating  carbon  dioxide,  oxygen,  and 
carbon  monoxide  in  producer-gases,  in  gases  from  blast- 
furnaces, and  from  other  sources. 

F.  Fischer  (DingL  polyt.  /.,  cclviii.,  p.  28)  has  employed  the 
Orsat  apparatus  for  estimating  the  acids  and  the  oxygen  in 
pyrites-kiln  gases,  for  which  purpose  he  charged  the  apparatus 
with  petroleum  in  lieu  of  water,  but  this  method  is  hardly  used 
by  practical  men. 


LUNGE'S  MODIFICATION  OF  THE  ORSAT 
APPARATUS. 

This  modification  (described  in  Chem.  Ind.>  1882,  p.  77; 
DingL  polyt.  /".,  ccxlv.  p.  512),  in  addition  to  all  the 
essential  parts  of  an  ordinary  Orsat  apparatus,  contains  a 
contrivance  for  burning  hydrogen  (and  other  gases)  by  means  of 
heated  palladium  asbestos  or  palladium  wire. 

It  is  shown  in  Fig.  43.  a  is  the  gas-burette,  £,  c,  and  d  are 
the  usual  (J-tubes  for  absorbing  carbon  dioxide,  oxygen,  and 
carbon  monoxide ;  k  is  the  ordinary  three-way  cock ;  e  is  an 
additional  glass  tap,  to  which  is  fused  a  capillary  tube,  bent 
twice  at  a  right  angle.  This  is  tightly  joined  by  stout  india- 
rubber  tubing  to  the  combustion-capillary  tube/,  which  contains 
a  thread  of  palladium  asbestos,  the  preparation  of  which  will  be 
described  later  on,  and  which  can  be  heated  by  means  of  the 
small  spirit-lamp  g,  fixed  in  a  spring  clamp  which,  by  means  of 
the  pivot-wire  /,  turns  in  a  socket  fastened  to  the  wooden  case, 
containing  the  apparatus.  The  IJ-tube  h  is  exactly  similar  to 


72 


TECHNICAL  GAS-ANALYSIS 


the  tubes  b,  c,  and  d,  and  is  filled  with  water  up  to  its  capillary 
neck.  The  dotted  |J-tuke  shown  at  the  left  is  filled  with  cotton- 
wool, and  serves  for  retaining  any  tarry  matters,  soot,  etc. 

The  apparatus   is    manipulated   as   follows  .-—First   carbon 


FIG.  43. 

dioxide,  oxygen,  and  carbon  monoxide  are  absorbed  in  the 
usual  manner,  described  supra,  p.  64.  (If,  however,  there  is  but 
little  carbon  monoxide  present,  say  not  exceeding  2  or  3  per 
cent.,  it  is  preferable  to  omit  the  treatment  of  the  gas  with 
cuprous  chloride  solution,  and  to  burn  the  carbon  monoxide, 
the  percentage  of  which  is  found  by  a  special  experiment. 


ORSAT-LUNGE  APPARATUS  73 

together  with  the  hydrogen.  Any  ethylene  present  would 
be  absorbed  by  the  cuprous  chloride  together  with  the 
carbon  monoxide.)  Now  air  is  admitted  through  the  three- 
way  cock  k,  and  lowering  the  level-bottle  connected  with  a  to 
the  gaseous  residue  contained  in  a,  until  the  water  goes  down 
nearly  to  the  zero  mark  in  a,  so  that  the  total  volume  of  gas  in 
a  is  nearly  100  c.c.  The  air  thus  introduced  will  allow  of 
burning  a  quantity  of  hydrogen  corresponding  to  two-fifths  of 
its  volume  (z>.,  twice  the  volume  of  oxygen  contained  in  the 
air).  This  is  sufficient  for  ordinary  producer-gas  ("  Siemens 
gas ") ;  but  when  analysing  water-gas  or  similar  mixtures 
containing  a  considerable  quantity  of  hydrogen,  one  of  the 
following  modes  of  proceeding  must  be  adopted.  Either  less  than 
looc.c.  of  the  gas  must  be  employed  for  analysis  ;  or  if  employing 
JOOC.G.  ofgas  after  the  first  combustion  has  taken  place,  and 
the  contraction  of  volume  has  been  noted,  another  quantity  of 
air  is  introduced  and  the  combustion  is  repeated  ;  or,  thirdly, 
oxygen  in  lieu  of  air  is  introduced  through  k,  which  necessitates 
only  one  combustion. 

After  reading  off  the  volume  of  gas  contained  in  a  and  the 
volume  after  admission  of  air  (or  oxygen),  the  spirit-lamp  £•  is 
lighted  and  the  capillary  /  is  very  gently  heated ;  then  the 
level-bottle  is  raised,  tap  e  is  opened,  and  the  gas  is  passed 
from  a  through  the  capillary  /  into  the  pipette  h  and  back 
again  into  a.  During  this  operation  one  end  of  the  palladium- 
asbestos  thread,  that  opposite  to  the  current  of  gas,  should 
become  red-hot.  The  volume  ofgas  in  a  is  measured,  and  the 
passage  of  the  gas  through /is  repeated.  If  (which  is  usually 
not  the  case)  a  further  contraction  is  now  observed,  the  passage 
of  the  gas  through /must  be  repeated  once  more.  The  residual 
gas  is  now  finally  measured,  and  two-thirds  of  the  diminution 
of  volume  calculated  as  hydrogen. 

In  the  case  of  a  very  high  percentage  of  hydrogen,  e.g.  in 
water-gas,  the  oxygen  of  the  air  introduced  will  not  suffice  for 
burning  all  the  hydrogen.  In  such  cases  it  is  preferable,  as 
stated  above,  to  employ  oxygen  for  the  combustion.  If  this 
has  not  been  done,  the  fact  of  the  volume  of  the  residual  gas 
in  a  remaining  constant  after  passing  it  twice  through  /  is  not 
caused  by  the  complete  removal  of  hydrogen,  but  by  that  of 
oxygen.  To  make  sure  of  this,  a  fresh  quantity  of  air  is  mixed 


74  TECHNICAL  GAS-ANALYSIS 

with  the  residual  gas,  and  it  is  observed  whether  a  further  con- 
traction takes  place  after  passing  the  mixture  through/! 

The  principal  application  of  this  apparatus  is  the  estimation 
of  free  hydrogen  along  with  carbon  dioxide,  oxygen,  and  carbon 
monoxide  in  producer-gas,  water-gas,  and  similar  mixtures.  It 
is  much  more  portable  than  Hempel's  burette  with  its  append- 
ages, and  the  tests  can  be  made  in  any  locality  and  very 
quickly.  Ethylene  and  other  heavy  hydrocarbons  would  be 
absorbed  by  the  cuprous  chloride,  together  with  carbon 
monoxide ;  but  they  occur  in  such  gases  in  quantities  so  small 
that  they  may  be  safely  neglected,  or  rather  calculated  as 
carbon  monoxide.  If,  however,  they  are  to  be  accounted  for,  a 
second  test  should  be  made,  leaving  out  the  operation  with 
cuprous  chloride ;  this  time  the  gas,  after  carbon  dioxide  and 
oxygen  have  been  observed  in  the  usual  way,  is  at  once  mixed 
with  an  excess  of  air  and  burnt  by  the  palladium-asbestos.  By 
measuring  the  contraction  produced,  then  absorbing  the  CO2 
by  the  receiver  b  filled  with  caustic-potash  solution,  and 
measuring  the  new  diminution  of  volume,  we  obtain  another 
estimation  of  the  combustible  gases  (carbon  monoxide,  hydrogen, 
and  ethylene)  in  the  following  way : — If  the  first  contraction  is 
diminished  by  one-half  of  the  second  contraction  (that  is  that 
which  takes  place  by  absorption  of  the  CO2  formed  in  the 
combustion  process),  two-thirds  of  the  difference  represent  the 
hydrogen ;  the  carbon  monoxide  corresponds  to  the  second 
contraction,  according  to  the  following  formulae : — 


2x  vols  CO  +  x  vols  O  yield  2X  vols  CO2. 
2y  vols  H  +y  vols  O  yield  (condensed)  H2O. 


Hence  : — 


First   contraction  (A)  = 
Second         „          (B)  =  2x. 


It  follows  from  this  that  the  carbon  monoxide  in  the  gas 

A- ?. 
analysed  is  =  B,  and  the  hydrogen  =  2 

O 

If  the  numbers  thus  obtained  agree  closely  with  those  found 
by  the  first  test  made  in  the  ordinary  way  as  described  supra, 
p.  72,  we  may  conclude  that  no  heavy  hydrocarbons  were 


ORSAT-LUNGE  APPARATUS  75 

present ;  indeed  we  must  expect  to  find  rather  less  CO2  than 
demanded  by  theory,  as  part  of  it  will  be  absorbed  by  the  water 
contained  in  the  apparatus  (in  order  to  diminish  this  error, 
the  analysis  should  be  performed  as  rapidly  as  possible).  If, 
therefore,  the  CO2  is  in  excess  of  that  required  on  the 
assumption  that  only  CO  and  H  were  present,  we  must  conclude 
that  heavy  hydrocarbons  were  present.  Equations  might  be 
given  for  calculating  these,  but  their  estimation  in  this  way 
would  not  be  very  correct,  so  that  we  prefer  leaving  it  aside. 
Ethylene  by  itself  may  be  previously  absorbed  by  bromine 
water,  as  we  shall  see  in  a  later  chapter. 

Any  methane  present  in  the  original  gas  will  not  be  touched 
by  the  previously  described  operations ;  it  remains  with  the 
nitrogen  in  the  last  remaining  gas.  We  shall  see  later  on  that 
methane  can  be  burned  by  means  of  a  strongly  heated  platinum 
capillary,  and  such  a  capillary  may  also  be  employed  in  the 
Orsat-Lunge  apparatus,  in  the  place  of  the  palladium-asbestos 
capillary,  if  that  apparatus  is  to  be  used  for  the  analysis  of 
water-gas  or  producer-gas,  where  heavy  hydrocarbons  need  not 
be  taken  into  account. 

In  the  case  of  gases  containing  much  carbon  monoxide  the 
absorption  of  this  constituent  by  cuprous  chloride  is  sometimes 
incomplete,  and  the  carbon  monoxide  left  unabsorbed  is  burned 
afterwards  in  the  treatment  just  described,  together  with  the 
hydrogen.  If  this  is  suspected  the  gas  remaining  in  a  must  be 
passed  into  b,  in  order  to  take  out  the  carbon  dioxide  formed  in 
the  combustion  of  carbon  monoxide,  and  the  residual  gas  is 
finally  measured  in  a.  The  contraction  produced  by  this  last 
operation  is  =  the  volume  of  carbon  monoxide  left  unabsorbed 
by  cuprous  chloride. 

Suppose  a  producer  -  gas  to  have  given  the  following 
readings : — 

1.  After  absorbing  the  carbon  dioxide       .  .     a  contraction  of   3-2  c.c. 

2.  „  „  oxygen       .          . .  .  no  contraction 

3.  ,,  ,,  carbon  monoxide  .  .     a  contraction  of  24-2  c.c. 

4.  After  mixing  with  air  for  combustion    .  .  ,,  0-9    „ 

(That  is,  adding  24-2-0-9  =  23-3  c.c.  air) 

5.  After  burning  the  mixture  by  the  palladium     .  „  108    „ 


6.      „      absorbing  the  CO2  formed  from  the  CO, 
unabsorbed  in  No,  3,  by  the  process  No.  4 


1 1-4 


76  TECHNICAL  GAS-ANALYSIS 

That  means  that  in  No.  3,  24-2  — 3-2  =  21-0  per  cent  carbon 
monoxide  had  been  absorbed ;  from  No.  6  it  follows  that 
11-4—10-8  =  0-6  must  be  added  to  this,  bringing  up  the  total 
percentage  of  carbon  monoxide  to  2 1  -6  per  cent.  The  contraction 
of  volume  after  burning  the  residual  gas  and  deducting  the  CO 
present  in  this  (the  volume  of  CO2  formed  is  exactly  equal  to 
that  of  the  CO  burned)  is  10-5,  two-thirds  of  which  =  7  percent., 
less  the  0-6  per  cent,  carbon  monoxide  unabsorbed  =  6-4,  is  the 
original  percentage  of  hydrogen.  Hence  the  composition  of 
the  original  gas  is — 

Carbon  dioxide     .  .  .        3-2  per  cent. 

Oxygen      .  .         •    .  .  none 

Carbon  monoxide  .         .  .  •     21*6  per  cent. 

Hydrogen  .  .  .6-4        „ 

Nitrogen  (with  a  little  methane)        68-8        „ 

100-0  per  cent. 


FURTHER  MODIFICATIONS  OF  THE  ORSAT 
APPARATUS. 

The  chemical  literature  contains  a  great  many  descriptions 
of  various  forms  of  apparatus  of  this  class,  both  for  the  rapid 
examination  of  producer-  or  smoke-gases,  and  for  the  analysis 
of  more  complicated  gaseous  mixtures.  Many  of  these  are 
not  obtainable  in  commerce.  We  here  enumerate  briefly  the 
more  important  apparatus  of  this  class. 

Gebhardt's  gas-analyser  (Chem.  Zeit.,  1907,  p.  283,  sold  by 

A.  Primavesi,  Magdeburg)   serves  for  estimating  the  excess  of 
oxygen    in  fire-gases.     It   consists  of  a  measuring  burette,  an 
absorbing    vessel    filled    with    phosphorus,    and    an    absorbing 
bottle  with  india-rubber  pumps. 

Strohlein  &  Co.  at  Diisseldorf  (Z.  fur  chem.  Apparalenkunde, 
1907,  p.  323)  describe  an  apparatus  for  estimating  carbon 
dioxide  in  smoke-gases.  The  gas  to  be  tested  forces  a  certain 
quantity  of  caustic  solution,  through  which  it  passes,  into 
a  measuring  vessel,  where  the  percentage  of  CO2  can  be  directly 
read  ofT. 

The  apparatus  of  Sodeau  (Chem.  News,  1904,  Ixxxix.  p.  61  ; 

B.  P.  12225    of  1906,  sold  by  Brady  &  Martin,  Newcastle-on- 
Tyne)    is    also    especially   applicable   to   the    examination    of 


MODIFIED  OKSAT  APPARATUS 


77 


chimney-gases.  Instead  of  the  cuprous  chloride  pipette  and 
the  palladium  -  combustion  tube  it  contains  a  combustion 
apparatus,  consisting  of  two  separate  vessels,  the  bulb  O  and 
the  aspirator  CR,  as  shown  in  Fig.  44 ;  or  it  may  be  shaped  like 
a  Hempel  pipette  for  solid  absorbents,  as  shown  infra,  Fig.  51, 
p.  85,  provided  with  a  straight  instead  of  with  a  bent  capillary 
tube.  The  bulb  O  contains  a  platinum  wire,  0-25  to  0-3  mm. 


FIG.  44. 

in  diameter,  attached  to  brass  electrodes,  and  is  heated  by 
a  current  of  5  amperes.  The  lens  L  affords  increased  accuracy 
in  reading.  Pipettes  K  and  P  serve  for  the  determination  of 
carbon  dioxide  and  oxygen.  CR  is  a  movable  reservoir  for 
the  rapid  joint  estimation  of  carbon  monoxide  and  hydrogen 
(a  more  detailed  description  is  given  in  Lunge-Keane's  Technical 
Methods  of  Chemical  Analysis,  vol.  i.,  part  I,  pp.  203  et  seq.\ 
on  pp.  219  et  seq.  another  apparatus  of  Sodeau  is  fully  described). 
The  apparatus  of  Babb  (/.  Amer.  Chem.  Soc.,  1905,  xxvii. 
p.  156)  comprises  six  absorbing  pipettes,  holding  250  c.c.  each, 


78 


TECHNICAL  GAS-ANALYSIS 


n 


\ 


— c 


— s 


an  explosion  tube,  two  dry  batteries,  an  induction  coil,  and  two 
level  bottles.  The  absorbing  pipettes  are  so  constructed  that 
the  gas  must  traverse  the  absorbing  liquid.  Bement  (ibid., 

p.  1252)  adds  to  this 
apparatus  an  india-rub- 
ber pump  for  squirting 
the  absorbing  liquid  into 
the  gas. 

Earnhardt  and  Rand- 

T^      1    |p\  all  (Z.furchem.Appar- 

f      \  iFlllFl  atenkunde,  1908,  p.  337) 

describe  an  Orsat  ap- 
paratus in  which  the 
measuring-tube  is  closed 
at  the  top  by  a  six-way 
cock,  to  the  capillary 
tubes  of  which  the 
absorbing  pipettes  are 
radially  joined. 

Siebert  and  Kiihn,  of 
Cassel,  sell  an  apparatus 
made  on  the  place  of 
the  Gasmotorenfabrik 
Deutz,  containing  four 
absorbing  pipettes  of 
special  construction 
which  turn  on  a  brass 
plate,  so  as  to  be  con- 
nected in  rotation  with 
the  burette. 

The  apparatus  of  Wencelius  (Stahl  u.  Risen,  1902,  p.  664; 
sold  by  Strohlein  &  Co.,  of  Diisseldorf )  contains  two  burettes, 
holding  100  c.c.  each,  one  of  them  for  readings  from  o  to  50,  the 
other  from  50  to  100  c.c.,  and  absorbing  pipettes  for  carbon 
dioxide  and  oxygen. 

L.  M.  Dennis  (/.  2nd.  and  Engin.  Chem.^  Dec.  1912) 
describes  an  absorption  bottle  shown  in  Fig.  45.  The  gas 
mixture  enters  the  pipette  through  the  capillary  A  (the  stop- 
cock being  in  position  I),  and  passing  downward  through  the 
capillary,  escapes  at  B.  It  then  rises,  and  in  so  doing  follows 


FIG.  45. 


MODIFIED  ORSAT  APPARATUS  79 

the  spiral  S.  The  rising  gas  carries  some  of  the  absorbing 
liquid  with  it,  and  this  liquid  then  flows  down  on  the  inside 
of  the  cylinder  C  and  mixes  with  the  main  body  of  the 
absorbent  again  at  D.  After  the  gas  has  risen  through  the 
spiral  and  has  collected  in  the  space  F,  the  stopcock  is  turned 
through  1 80°  to  position  II,  and  the  gas  is  then  drawn  back 
into  the  burette. 

The  same  author  (Gas- Analysis,  1913,  pp.  90  et  seq.)  describes 
the  modifications  of  the  Hempel  apparatus,  where  it  is  intended 
for  exact  gas-analysis,  with  mercury  as  confining  liquid. 

Dennis  points  out  several  drawbacks  connected  with  the 
use  of  the  ordinary  Orsat  apparatus,  such  as  the  incorrect 
position  of  the  measuring  burette,  etc.  To  avoid  these,  he  has 
designed  the  modification  shown  in  Fig.  46,  which  is  manu- 
factured by  Greiner  &  Friedrichs,  Stiitzerbach  in  Thiiringen 
(Germany).  The  burette  B  has  a  capacity  of  somewhat  more 
than  100  c.c.,  and  is  graduated  from  a  point  near  the  bottom 
upward  to  the  stopcock  J.  This  is  a  three-way  stopcock,  the 
position  of  which  is  shown  by  means  of  a  black  glass  H  fused 
to  its  outer  surface.  The  capillary  tube  connecting  J  with  the 
pipettes  and  with  the  stopcock  K  has  an  external  diameter  of 
7  mm.  and  an  internal  diameter  of  I  mm.  In  fusing  on  the 
branch  capillaries  which  extend  downward  to  the  three  pipettes, 
the  internal  diameter  of  the  capillary  should,  at  no  point,  be 
much  greater  than  I  mm.  if  the  apparatus  is  properly  made. 
The  three  absorption  pipettes,  E,  F,  and  G,  are  of  the  form 
already  described,  and  are  filled,  respectively,  with  solutions 
of  potassium  hydroxide,  alkaline  pyrogallol,  and  ammoniacal 
cuprous  chloride.  They  are  connected  with  the  capillary  tube 
from  the  burette  by  means  of  pieces  of  soft,  black  rubber  tubing 
of  1-5  mm.  thickness  of  wall,  and  these  rubber  tubes  are  held  in 
place  by  wire  hooks  that  pass  through  the  blocks  behind  the 
joints,  and  have  threaded  ends  upon  which  small  set  screws  are 
placed.  This  method  of  attachment  renders  it  easily  possible 
to  remove  all  the  glass  parts  from  the  frame.  Into  the  open 
ends  of  the  three  level-tubes  of  the  pipettes  are  inserted  one- 
hole  rubber  stoppers,  and  through  the  openings  of  these  stoppers 
pass  the  branch-tubes  from  the  tube  SS,  that  is  J  mm.  external 
diameter  and  I  mm.  thickness  of  wall.  This  tube  passes  down- 
ward and  is  joined  by  a  piece  of  rubber  tubing  to  the  upper 


80  TECHNICAL  GAS-ANALYSIS 

side  of  the  stopcock  attached  to  the  cylindrical  vessel  T,  which 
in  turn  is  connected  with  V  by  the  glass  tube  shown  by  the 
dotted  line.  After  the  pipettes  have  been  filled  with  the 
several  reagents,  the  stoppers  connecting  the  level-tubes  with 


FIG.  46. 

the  tube  SS  are  inserted  in  place,  and  the  protecting  reservoir 
VT  is  half  filled  with  water.  As  the  gas  is  driven  over  from 
the  burette  into  the  pipette  and  is  drawn  back  into  the  burette, 
the  water  in  VT  rises  and  falls,  but  protects  the  reagents  at  all 
times  from  contact  with  the  air.  The  level-bottle  L  is  held  in 
place  by  a  clamp  when  the  apparatus  is  in  transport. 


MODIFIED  ORSAT  APPARATUS 


81 


After  the  absorbable  gases  have  been  removed  from  the 
gas  mixture,  the  combustible  residue  may  be  burned,  if  so 
desired,  by  connecting  the  capillary  M,  which  has  an  external 
diameter  of  6  mm.  and  a  bore  of  I  mm.,  with  a  combustion 
pipette  or  other  suitable  device.  The  case  containing  the 
apparatus  is  57  cm.  high,  27  cm.  wide,  and  16  cm.  deep.  The 
panels  forming  the  front  and  back  of  the  case  are  removed 
when  the  apparatus  is  in  use.  As  illustrative  of  the  speed, 
accuracy,  and  uniformity  of  the  results  yielded  by  this  apparatus, 
the  following  analyses  of  a  mixture  of  carbon  dioxide,  oxygen, 
and  carbon  monoxide  may  be  cited.  A  single  passage  of  the 
gas  mixture  in  one  minute  into  the  first  absorption  pipette 
serves  to  completely  remove  the  carbon  dioxide.  In  the 
determination  of  oxygen  and  carbon  monoxide  each  gas  was 
twice  passed  into  the  absorption  pipette,  the  first  time  in  two 
minutes,  the  second  time  in  one  minute. 


I. 

II. 

III. 

IV. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Carbon  dioxide    . 

3'I 

3-1 

3-2 

3'I 

Oxygen 

6-0 

6-0 

5-9 

5'9 

Carbon  monoxide 

22-5 

22-6 

22-6 

22-7 

Further  modifications  of  the  Orsat  apparatus  have  been 
described  by : 

Thorner  (Chem.  Zeit.,  1891,  p.  768). 

Hankus  (Oesterr.  Z.  f.  Berg  u.  Huttenwesen,  1899,  p.  81  ; 
Stahlu.  Eisen,  1903,  p.  261). 

Fieber  (Chem.  Zeit.,  1905,  p.  80). 

Neumann  (ibid.,  1905,  p.  1128). 

Wilhelmi  (Z.  angew.  Chem.,  1911,  p.  870). 

Lomschakow  (sold  by  Ludwig  Mohren,  of  Aix-la-Chapelle). 

Preuss  (Z.  angew.  Chem.,  1912,  p.  2112). 

Bendemann  (/.  Gasbeleucht.,  1906,  p.  853). 

Rowicki    (Oesterr.    Z.  f.    Berg    u.    Huttenwesen,    1905,    p. 

337). 

Heinz  (/.  Gasbeleucht.,  1905,  p.  367). 

Harm  (Z.  Verein.  deutsch.  Ingen.,  1906,  p.  212  ;  1911,  p.  472  ; 
I9l$i  P-  9545  /•/  Gasbeleucht.,  1906,  pp.  367  and  474;  1911, 
p.  472). 

F 


82 


TECHNICAL  GAS-ANALYSIS 


HEMPEL'S   APPARATUS. 

These  apparatus  (described  by  Hernpel  in  his  treatise  Ueber 
technische  Gasanalyse,  1877,  and  Gasanalytische  Methoden,  4th 
ed.,  1900,  p.  29)  have  proved  most  useful  and  have  acquired 

a  large  radius  of  appli- 
cation. Hempel  started 
by  modifying  the  "  gas- 
pipettes,"  previously  de- 
scribed by  Ettling  and 
Doyere  for  the  separate 
absorption  and  estimation 
of  the  single  constituents 
of  a  gaseous  mixture, 
which  are  attached  to  a 
gas-burette  by  means  of 
a  connecting  capillary. 
This  secures  the  advan- 
tage that  the  measuring 
of  the  gas  and  its  treat- 
ment with  the  various 
absorbents  can  be  separ- 
ately performed  at  leisure 
and  in  a  very  efficient 
way,  with  a  high  degree 
of  accuracy,  and  employ- 
ing water  as  a  confining 
liquid. 

The  ordinary  Hempel's 
gas-burette  is  shown  in 
Fig.  47,  in  connection 
with  an  absorbing-pipette. 
It  consists  of  two  cylin- 
drical glass  tubes,  A  and 
"FIG. 47.  B,  1-5  cm.  wide  and  55 

to    68    cm.    long,   whose 

bottom  ends  are  contracted  and  turned  in  a  right  angle. 
These  tubes  are  cemented  into  stands  made  of  thin  cast- 
iron  or  of  polished  black  wood,  their  contracted  ends  passing 


HEMPEL'S  APPARATUS 


83 


out    sideways   at   a    right   angle.      The   bottom    outlets    have 

an   outside    diameter   of  4    mm.  ;    they  are  thickened   at   the 

outer  end,  so  that   they  can  be  easily  and  tightly  connected 

with   an    india-rubber   tube,    about    120    cm.    long,   which    is 

preferably    interrupted    in    the    middle    by    a    piece   of  glass 

tubing,  and  which   allows  of   placing   the   tubes    at   a  higher 

or   lower   level.     The   measuring-tube  A  at   the   top   ends   in 

a  thick  capillary,  0-5  to  I  mm.  wide,  and  3  cm.  long,  upon  which 

a   piece   of    thick    india-rubber    tubing,   2    mm.   bore,  6   mm. 

outside  diameter,  and  5  cm- 

long,    is    drawn    and    fixed 

gas-tight  by  means  of  a  silk- 

covered  copper  wire.  Closely 

above  the  capillary  the  elastic 

tube   is  closed    by   a    small 

pinchcock,  which  is  taken  off 

when  not  required   for  use. 

From  this  top  end  down  to 

the  bottom  mark,  3  or  4  cm. 

above  the  foot,  tube  A  holds 

100  c.c.,  divided  into   fifths 

of  a  cubic   centimetre,  and 

showing    on    one    side    the 

figures  from  o  to  100,  on  the 

other  from    100   to  o.     The 

level-tube  B  is  a  plain  glass 

tube,  open  at  the  top. 

In  lieu  of  this,  burettes 
with  a  water-jacket  may  be 
used,  as  shown  in  Fig.  48. 
This  jacket,  3  cm.wide,  serves 

for  keeping  the  temperature  of  the  gas  constant  ;  it  is  provided 
at  top  and  bottom  with  side-branches  through  which,  if  needed, 
water  may  be  run  in  a  constant  stream.  The  burette  is  fixed 
in  this  water-jacket  by  means  of  india-rubber  corks.  In  most 
cases  these  jackets,  which  make  the  apparatus  less  handy, 
are  not  required. 

For  the  analysis  of  gaseous  mixtures  which  cannot  be 
confined  over  water,  because  some  of  their  constituents  are 
too  easily  absorbed  by  it,  Hempel  employs  what  is  called 


p,G 


84 


TECHNICAL  GAS-ANALYSIS 


the  modified  Winkler's  gas-burette,  Fig.  49.  This  is  at  the 
bottom  closed  by  a  three-way  glass  tap  c,  and  at  the  top  by  a 
simple  glass  tap  d  or  by  a  pinchcock  ;  the  space  between  these 
taps  contains  100  c.c.,  divided  into  fifths.  Before  introducing  the 
gas,  the  measuring-tube  b  must  be  completely  dried,  e.g.,  by 
rinsing  it  first  with  alcohol,  then  with  ether, 
and  then  blowing  a  rapid  current  of  air 
through  it.  It  is  charged  with  the  gas  by 
passing  this  through  it  until  all  the  air  has 
been  expelled,  for  which  purpose  the  pinch- 
cock  attached  to  c  is  connected  with  the 
source  of  the  gas,  and  the  tap  d  with  an 
aspirator,  or  vice  versa.  Otherwise  this 
apparatus  is  arranged  and  manipulated  like 
an  ordinary  Hem  pel  burette. 

Absorption-pipettes. — Various  such  pipettes 
belong  to  the  Hempel  apparatus.  In  Fig.  47 
(supra,  p.  82)  is  shown  what  is  called  the 
simple  absorption-pipette.  It  consists  of  two 
glass  bulbs,  a  and  b,  fixed  on  a  wooden  or 
iron  stand,  and  communicating  by  a  bent 
tube.  Bulb  a  is  connected  with  the  thick- 
walled  capillary  |J-tube,  0-5  to  I  mm.  bore, 
projecting  a  centimetre  or  two  over  the  stand 
and  ending  in  a  piece  of  india-rubber  tubing. 
This  is  closed  by  a  short  glass  rod  when  the 
pipette  is  not  in  use,  and  by  a  pinchcock 
when  this  is  the  case.  Bulb  a  holds  150  c.c., 
bulb  b  100  c.c.,  so  that  when  a  is  charged 
with  100  c.c.  of  gas,  there  is  still  room  for 
the  absorbing  liquid.  Behind  the  capillary 
(J-tube  a  white  porcelain  slab  is  fixed  for  the  purpose  of 
making  the  liquid  thread  more  easily  visible.  The  india-rubber 
tubes  must  be  of  the  best  quality,  and  must  be  fastened  on  by 
thin  wire  in  order  to  prevent  leakages  and  other  trouble.  The 
absorbing  liquid  is  poured  into  the  wide  tube  attached  to  b, 
carefully  sucking  out  the  air  from  a  through  the  capillary  tube. 
This  is  done  until  the  liquid  has  completely  filled  bulb  a  and 
has  entered  into  the  capillary ;  bulb  a  must  be  nearly  empty. 
As  stated  above,  the  capillary  (J-tube  of  a  is  during  use 


FIG.  49. 


HEMPEL'S  APPARATUS 


85 


closed  by  an  elastic  tube  and  pinchcock.  When  it  is  to  be  put 
out  of  use,  the  piece  of  glass  rod  is  put  into  the  outside  end  of 
the  elastic  tube,  while  the  pinchcock  is  closed,  and  this  cock 
is  only  removed  subsequently  ;  otherwise  on  putting  in  the  glass 
rod,  air  would  be  forced  in  and  the  thin  column  of  liquid  in  the 
U-tube  may  be  broken.  Should  this  happen  anyhow,  the 
capillary  tube  is  emptied  by  sucking  for  a  moment  at  a,  and 
filled  again  by  blowing  air  in  the  opposite  direction.  The  end 
of  the  tube  coming  out  of  bulb  b,  when  the  pipette  is  not  in  use, 
is  closed  by  a  cork,  which  must  be  removed  before  using  the 
pipette. 

Fig.    50  shows   the    pipette   employed   when  using  fuming 
oil  of  vitriol  as  an  absorbing  liquid.     Here  bulb  a  is  surmounted 


FIG.  50. 


FIG.  51. 


by  a  smaller  bulb,  d,  filled  with  small  bits  of  glass,  which 
enlarges  the  absorbing  surface  and  renders  agitation  un- 
necessary. The  ends  of  this  pipette  are  closed  by  small  glass 
caps,  which  may  be  made  quite  tight  by  means  of  small  india- 
rubber  rings. 

A  pipette  for  the  use  tf  solid  reagents,  the  "tubulated  absorption- 
pipette"  is  shown  in  Fig.  51.  Here,  instead  of  a  bulb  there  is  a 
cylindrical  part  a,  with  a  neck  at  the  bottom.  Through  this  the 
solid  reagent — e.g.  sticks  of  phosphorus — is  put  in  together  with 
water,  whereupon  the  neck  is  closed  by  a  soft  india-rubber 
stopper,  and  the  pipette  is  placed  in  the  proper  position.  The 


86 


TECHNICAL  GAS-ANALYSIS 


tube  over  bulb  e  may  be  connected  with  another  pair  of  bulbs, 
as  shown  in  Fig.  52,  where  this  is  necessary. 

The  composite  absorption  pipette,  Fig.  52,  is  used  for 
absorbents  which  suffer  change  in  contact  with  atmospheric 
air,  such  as  the  alkaline  solution  of  pyrogallol,  or  the  hydro- 
chloric or  ammoniacal  acid  solution  of  cuprous  chloride ;  also 
for  such  as  give  off  irritating  vapours,  like  bromine  water. 


FIG.  52. 

Here  a  second  pair  of  bulbs,  c  and  d,  form  a  water  lute, 
excluding  the  contact  with  the  outside  air.  These  pipettes 
must  be  filled  through  the  capillary  U-tuDe  in  connection  with 
bulb  a,  by  connecting  its  india-rubber  end  with  a  funnel-tube  of 
about  a  metre  in  length,  through  which  the  absorbing  liquid 
is  poured. 

Fig.  53  shows  an  improvement  in  this  pipette,  consisting  in 
a  short  branch  attached  to  the  lowest  point  of  the  connecting 
tube  between  a  and  b,  closed  by  a  pinchcock  or  glass  rod,  for 
the  purpose  of  charging  the  pipette.  After  doing  so,  the 
pinchcock  is  replaced  by  a  glass  rod.  The  stand  is  cut  out 
accordingly. 

General  Arrangement  of  Hempel's  Apparatus. — The  general 
arrangement  is  shown  in  Fig.  47  (supra,  p.  82).  The  burette 
A  and  the  capillary  of  pipette  C,  after  putting  on  pinchcocks  as 
shown  in  the  drawing,  are  connected  by  the  glass  capillary  E, 
made  of  a  tube  18  cm.  long,  6  mm.  outside  diameter,  and  I  mm. 
bore,  by  bending  it  on  each  side  into  a  right  angle,  with  limbs 
4  or  4j  cm.  long,  the  ends  of  which  are  rounded  off.  The 


HEMPEL'S  APPARATUS 


87 


pipette  is  placed  on  a  wooden  bench,  about  46  cm.  high,  37  cm. 
long,  and  10  cm.  broad. 

A.  C.  Gumming  (/".  Soc.  Chem.  Ind.y  1913,  p.  9)  describes  a 
modification  of  the  Hempel  double  pipette,  which  he  provides 
with  a  special  tube  for  filling  with  the  reagent.  A  portable 
Hempel  apparatus  has  been  devised  by  L.  M.  Dennis  (Gas- 
Analysis,  1913,  p.  69). 


FIG.  53. 

The  remark  made  in  the  case  of  the  gas-volumeter  (supra, 
p.  27),  according  to  which  the  apparatus  should  be  placed  in 
a  room  of  nearly  constant  temperature,  since  a  fluctuation  of 
merely  i°  C.  causes  an  analytical  error  of  0-3  per  cent.,  applies 
equally  to  Hempel's  (like  most  other)  ordinary  apparatus  for 
gas-analysis,  but  this  is  avoided  by  the  water-jacketed  burette, 
shown  supra,  Fig.  48. 

Manipulation  of  the  Hempel  Apparatus.  —  Remove  the 
connecting  capillary  tube  E  (Fig.  47),  lift  up  the  level-tube  B 
(previously  filled  with  water)  with  one  hand,  and  with  the 
other  hand  open  the  pinchcock  of  the  burette  A  till  this  is  full 
and  the  water  begins  to  run  out.  Now  connect  the  india-rubber 
tube  of  the  pinchcock  with  the  aspirating-tube,  already  filled  with 
the  gas,  place  the  level-tube  B  on  the  floor  of  the  room,  and 
open  the  tap  again,  whereupon  the  water  flows  back  into  the 
level-tube  and  the  gas  is  drawn  into  the  burette.  Allow  a  little 
more  than  100  c.c.  gas  to  enter  into  A,  compress  this  by  raising  B, 


88  TECHNICAL  GAS-ANALYSIS 

until  the  water  has  risen  in  A  above  the  zero  mark,  compress 
the  connecting  elastic  tube  with  the  fingers  close  to  the  joint, 
place  B  again  lower,  and  by  cautiously  loosening  the  elastic 
tube,  allow  the  water  to  run  out  until  the  zero  mark  has  just 
been  reached.  Then  the  connecting  tube  being  still  compressed, 
open  the  pinchcock  of  burette  A  for  a  moment,  whereupon  the 
gas  contained  in  A  gives  up  its  surplus  pressure  and  assumes 
that  of  the  atmosphere.  The  burette  now  contains  exactly  100 
c.c.,  of  which  we  convince  ourselves  by  bringing  the  water  to  the 
same  level  in  A  and  B.  For  exact  measurements  it  is  necessary 
to  wait  a  little  for  the  water  to  run  down  completely,  and  in 
such  cases  it  is  more  convenient  not  to  employ  exactly  100  c.c. 
gas,  but  a  little  more  or  less  as  the  case  may  be ;  but  for 
ordinary  technical  estimations  it  is  preferable  to  employ  just 
100  c.c.  in  order  to  save  calculations. 

We  now  proceed  to  connect  the  absorbing-pipettes,  one 
after  the  other,  with  the  burette,  as  shown  in  Fig.  47.  For  this 
purpose  we  put  the  capillary  E,  already  connected  with  pipette 
C,  on  the  burette  A.  In  order  to  avoid  any  bubbles  of  air  to 
be  enclosed,  the  india-rubber  tube  above  the  pinchcock  of  A 
is  filled  with  water,  the  capillary  E  is  put  in,  whereby  it  is  com- 
pletely filled  with  liquid,  and  now  the  other  end  of  E  is  put  into 
the  india-rubber  tube  of  pipette  C,  which  is  at  the  same  time 
emptied  of  air  by  compressing  it  between  two  fingers.  If  now  the 
pinchcock  on  A  is  opened,  and  the  level-tube  B  is  raised  at  the 
same  time,  the  gas  is  forced  from  A  through  E  into  the  bulb  a 
of  pipette  C,  driving  its  liquid  contents  into  bulb  b.  When 
this  has  taken  place,  we  drive  about  0-5  c.c.  of  water  from  A 
through  E,  whereby  this  capillary  is  rinsed  out  and  freed  from 
any  absorbing  liquid  it  may  have  retained.  The  gas  is  now 
enclosed  between  two  liquids,  viz.,  the  absorbing  liquid  in  the 
pipette  C,  and  the  water  contained  in  the  capillary  E.  Now 
close  both  pinchcocks,  take  the  pipette  C  off,  and  bring  about 
the  absorption  of  the  gas  contained  in  bulb  a,  by  gently  (not 
violently)  shaking  the  pipette.  The  absorption  of  the  gas  by 
the  liquid  in  C  is  generally  finished  in  about  two  minutes, 
sometimes  even  more  rapidly,  e.g.  in  the  case  of  carbon  dioxide. 
Now  connect  C  again  with  capillary  E,  place  the  level-tube  B 
on  the  floor,  and,  by  cautiously  opening  both  pinchcocks,  cause 
the  unabsorbed  gas  to  re-enter  the  burette  A,  taking  care  that 


HEMPEL'S  APPARATUS  89 

the  absorbing  liquid  at  the  end  just  gets  into  the  end  limb  of 
the  capillary  belonging  to  C,  but  not  into  the  connecting 
capillary  E.  In  the  case  of  liquids  inclined  to  frothing,  such  as 
the  alkaline  solution  of  pyrogallol,  this  cannot  be  always 
avoided  ;  if,  in  consequence  of  this,  the  india-rubber  joints 
should  become  so  slippery  that  the  capillary  tube  will  not  hold 
fast,  but  slides  off,  the  joints  must  be  washed  with  water  (the 
pinchcocks  being  closed),  and  their  ends  moistened  with  a  little 
dilute  acetic  acid  introduced  into  the  end  of  the  elastic  tube. 

Now  the  pinchcocks  are  closed,  capillary  E  is  taken  off, 
the  open  ends  of  the  elastic  tubes  are  closed  by  their  glass  rods, 
the  level-tube  B  is  cautiously  raised  up  to  the  point  where 
both  levels  coincide  (as  shown  in  Fig.  49,  p.  84),  and,  after 
waiting  a  couple  of  minutes  for  the  water  to  run  down,  the 
reading  is  taken,  placing  the  liquid  level  in  the  same  plane  as 
the  eye  of  the  manipulator. 

In  the  same  way,  by  employing  different  pipettes,  a  second, 
third,  and  further  constituent  of  the  gaseous  mixture  can  be 
absorbed  and  estimated. 

The  principal  applications  of  the  Hempel  apparatus  are 
the  following : — 

(a)  Estimation  of  carbon  dioxide  in  mixtures  with  air,  in 
chimney-gases,    gases     from     blast-furnaces,    lime-kilns,    gas- 
producers,  etc.,  by  means  of  a  simple  absorption-pipette,  Fig. 
47,  filled  with  a  solution  of  caustic  potash. 

(b)  Estimation   of    oxygen    in    atmospheric    air,    chimney- 
gases,  producer-gases,   etc.     This   takes  place  after   removing 
the  carbon  dioxide  as  mentioned  sub  a,  either  by  means  of  a 
concentrated   alkaline   solution   of  pyrogallol,   employed   in    a 
composite    absorption-pipette,    Fig.    52,     or    by   means   of    a 
tubulated  absorption-pipette,  Fig.  51,  filled  with  small  rolls  of 
copper  wire  gauze,  immersed   in  liquor  ammoniac ;  or  else  as 
well  in  the  presence  of  carbon  dioxide,  by  such  a  pipette  filled 
with  thin  sticks  of  phosphorus  under  water. 

(c)  Estimation   of  carbon   monoxide   in  producer-gas,  blast- 
furnace   gas,    chimney-gases,    etc.     After    absorbing    carbon 
dioxide  and  oxygen,  the  carbon  monoxide  is  absorbed  by  an 
ammoniacal  or  hydrochloric  acid  solution  of  cuprous  chloride, 
which  must  be  employed   in  a  composite  absorption  pipette, 
Fig.  52,  supra,  p.  86. 


90  TECHNICAL  GAS-ANALYSIS 

(d)  Estimation   of  hydrogen   by  combustion    with   oxygen, 
either  over  palladium-asbestos  or  by  explosion.      The  former 
method  is  carried  out  by  replacing   the  connecting  capillary 
tube    E,   Fig.   47,   by   a  similar  tube   containing   a  thread  of 
asbestos    fibre,    coated    with    metallic    palladium,   as   will   be 
described    in   a   following    chapter,   and    heated   as   described 
supra ,  p.  75,  in  connection  with  the  Lunge-Orsat  apparatus. 

(e)  Estimation  of  methane.     This  is   always  performed  by 
combustion  with  oxygen,  either  by  explosion  or  by  a  heated 
platinum  wire ;  in  the  presence  of  hydrogen  this  gas  must  be 


FIG.  54. 

first  removed  by  palladium  sponge,  as  mentioned  sub  </,  and 
described  in  a  later  chapter.  For  the  determination  of  methane, 
Hempel  has  constructed  a  special  "explosion-pipette"  The 
earlier  form  of  this,  even  now  the  more  usual  form  for  technical 
gas-analysis,  is  shown  in  Fig.  54;  it  is  an  ordinary  simple 
pipette,  provided  with  platinum  electrodes  at  k  and  a  large 
greased  stopcock  at  d,  and  filled  with  water  or  dilute  solution 
of  potassium  hydroxide.  An  improved  form  of  pipette,  in 
which  mercury  is  used  as  confining  liquid,  is  shown  in  Fig.  55  ; 
here  the  second  bulb  of  the  pipette  is  replaced  by  a  level-bulb 
a,  attached  by  a  piece  of  stout  india-rubber  tubing.  It  is 
advantageous  to  have  a  small  stopcock  fitted  to  the  top  of 
the  capillary  tube  at  £,  so  that  the  mixture  of  gas  and  air  or 
oxygen  can  be  fired  without  risk  of  loss  by  leakage.  (The  whole 


HEMPEL'S  APPARATUS  91 

arrangement  of  HempePs  apparatus  will  be  described  later  on, 
in  the  chapter  on  the  Combustion  of  Gases.) 

To  carry  out  the  determination  of  methane,  the  gas  remain- 
ing after  removing  the  constituents  enumerated  sub  a,  b,  c,  dy  is 
syphoned  over  into  the  explosion  pipette,  the  necessary  quantity 
of  air  or  oxygen  added  in  the  same  manner  as  when  burning 
hydrogen  over  palladium  asbestos,  the  total  volume  measured 
and  passed  over  into  the  pipette,  where  it  is  mixed  by  gentle 
shaking ;  the  water  in  the  burette  is  syphoned  over,  until  the 
capillary  tube  of  the  burette  is  filled,  when  the  tap  at  c  (Figs. 

c 


FIG.  55. 

54  or  55)  is  closed.  The  pressure  on  the  mixture  is  slightly 
reduced  before  the  explosion,  by  lowering  the  pressure  bulb  a ; 
tap  d  is  then  closed,  and  the  gases  are  exploded  by  attaching 
the  terminals  of  a  small  Rubmkorff  coil  to  the  electrodes  of  the 
pipette.  After  the  combustion,  the  gas  is  syphoned  back  into 
the  burette,  and  the  carbon  dioxide  formed  is  determined  by 
absorption  with  caustic  potash. 

The  quantity  of  air  or  oxygen  to  be  added  for  the  com- 
bustion must  be  calculated  as  follows.  The  ratio  of  combustible 
to  incombustible  gases  must  be  no  less  than  26  and  no  more 
than  64  to  100,  in  order  to  be  sure  that  no  nitrogen  is 
simultaneously  oxidised  (Bunsen,  Gasometrische  Methoden,  2nd 
ed.,  p.  72).  A  good  working  proportion  is  50  :  100,  bearing 
in  mind  that  the  oxygen  required  theoretically  for  the 
combustion  of  the  methane,  according  to  the  equation  : 


92  TECHNICAL  GAS-ANALYSIS 

is  included  in  the  combustible  gases,  the  excess  forming  part 
of  the  incombustible  gases.  The  choice  between  air  and 
oxygen  will  accordingly  be  decided  by  the  volume  of  the 
gas  to  be  dealt  with  and  its  content  of  methane.  Oxygen 
from  the  ordinary  commercial  oxygen  cylinders  can  be 
conveniently  used,  the  percentage  of  real  oxygen  in  it  having 
been  previously  determined,  One-third  of  the  total  contraction, 
after  the  absorption  of  carbon  dioxide,  represents  the  volume 
of  methane  present  in  the  original  gas  mixture. 

Preferable  to  this  somewhat  risky  explosion  process  is 
the  combustion  of  methane  by  a  heated  platinum  wire.  Methane 
is  completely  burned,  without  explosion,  by  passing  it,  mixed 
with  oxygen,  over  a  heated  surface  of  platinum.  Winkler 


FIG.  56. 

(Z.  anal.  Chem.,  1889,  xxviii.  p.  269;  J.  Soc.  Chem.  Ind.>  1889, 
p.  570)  designed  a  modified  form  of  Hempel  pipette  for  this 
purpose,  in  which  a  small  platinum  spiral,  enclosed  in  the  bulb 
of  the  pipette,  is  heated  by  an  electric  current.  A  much  more 
convenient  device  for  this  method  of  determination  is  the 
Drehschmidt  capillary  tube  (Ber.,  1888,  p.  3245)  shown  in  Fig.  56. 
It  consists  of  a  seamless  platinum  tube,  20  cm.  long,  2  mm. 
thick,  and  07  mm.  internal  diameter,  containing  three  or  four 
pieces  of  platinum  wire.  Pieces  of  brass  tubing  are  soldered 
to  the  ends  of  the  platinum  tube,  to  form  connections  with 
the  burette  and  the  pipette.  Two  small  cooling  cylinders 
(through  which  water  is  made  to  flow),  also  made  of  brass,  are 
fixed  on  to  the  brass  tubes,  just  above  the  bend.  The  tube 
must  be  tested  before  use  to  make  sure  that  it  is  air-tight. 
For  this  purpose  the  tube  is  made  red-hot,  closed  at  one  end, 
and  through  the  other  end  air  is  forced  in  at  a  pressure  of 
about  0-3  m.  mercury.  If  the  tube  is  then  placed  under  water, 
any  leakages  are  indicated  by  bubbles  of  air  appearing  on  the 
water.  To  carry  out  the  combustion,  this  capillary  tube  is 
attached  by  rubber  connections  to  the  burette  and  to  a  pipette 


MODIFIED  HEMPEL  APPARATUS  93 

charged  with  caustic  potash  solution  in  the  usual  way,  and 
the  mixture  of  gas  (or  air)  is  obtained,  as  described  above. 
The  capillary  is  then  heated  to  a  bright  red  heat,  preferably 
by  a  flat-flamed  Bunsen  burner,  and  the  gaseous  mixture  is 
passed  twice  backwards  and  forwards  over  the  heated  platinum. 
The  reading  is  taken  after  a  final  absorption  in  the  potash 
pipette ;  one-third  of  the  total  contraction  represents  the 
methane  present. 

Formation  of  Oxides  of  Nitrogen  in  Combustion  Pipettes. — 
A.  H.  White  (/.  Amer.  Chem.  Soc.,  1901,  p.  476)  stated  that  oxides 
of  nitrogen  are  formed  when  hydrogen  is  burned  with  oxygen 
and  air  by  electrically  heated  platinum  ;  but  Rhodes  (as  quoted 
by  Dennis  in  Gas- Analysis,  p.  153)  found  that  this  is  not  the 
case  to  a  measurable  extent,  where  the  conditions  laid  down 
by  Dennis  and  Hopkins  (ibid.,  1899,  p.  388)  are  observed,  and 
that  is :  that  the  platinum  spiral  is  heated  only  to  dull  redness 
during  the  combustion,  and  is  kept  at  dull  redness  for  no 
longer  than  sixty  seconds  after  the  gases  have  been  introduced 
into  the  pipette. 

Several  modifications  of  Hempel's  apparatus  have  been 
described  by  other  chemists,  of  which  we  mention  the 
following : — 

Babbitt  in/.  Amer.  Chem.  Soc.,  1904,  xxvi.  p.  1026,  describes 
a  "  stationary "  Hempel  apparatus  devised  by  W.  J.  Knox,  in 
which  the  pipettes  are  suspended  on  a  horizontal  rod,  while 
the  burette  and  level-tube  are  fastened  to  a  vertical  rod  in 
such  a  manner  as  to  permit  free  lateral  motion. 

De  Voldere  (Z.furchem.  Apparatenkunde,  1907,11".  p.  344) 
instead  of  the  level-tube  b  of  the  Hempel  apparatus  employs 
a  level-bottle  with  a  lateral  tube,  and  instead  of  the  burette  a 
he  uses  a  Pfeiffer's  burette  (Z.  angew.  Chem.,  1907,  p.  22),  as  will 
be  described  later  on. 

Hill  (Proc.  Chem.  Soc.,  1908,  xxiv.  p.  95)  attaches  a  three- 
way  tap  to  the  downward  branch  of  the  connecting  capillary. 
So  does  Gawalowski  {Z.  anal.  Chem.,  1911,  p.  435)- 

Spencer  (Berl.  Ber.,  1909,  p.  1786)  recommends  a  special 
tap  for  the  connecting-tube  between  the  burette  and  the 
absorbing-pipettes,  in  order  to  fill  this  tube  with  liquid. 

Knowles  (B.  P.  27545  of  1910)  places  the  absorption- 
apparatus  on  a  hinged  support,  so  that  on  turning  this  support 


FIG.  57. 


FISCHER'S  APPARATUS  95 

into  a  specified  position,  the  beaker  containing  the  absorbent 
liquid  may  be  removed  and  recharged. 

Gockel  (/.  Gasbeleucht.,  1911,  p.  228)  places  in  HempeFs 
composite  pipette  (p.  86)  the  branch  tube,  intended  for  filling, 
at  the  top. 

Hiifner  (Ger.  P.  244335  ;  Z.  angew.  Chem.,  1912,  p.  1665) 
describes  an  apparatus  by  which  the  gas  is  always  measured 
under  atmospheric  pressure. 

Anderson  (Z.  ange^u.  Chem.,  1914,  i.  p.  23)  provides  the 
inlet-capillary  with  a  3  mm.  bulb,  to  retain  any  absorbing 
liquid  squirting  over. 

FERDINAND   FISCHER'S   APPARATUS. 

This  apparatus  (Z.  angew.  Chem.,  1890,  p.  591)  has  been 
specially  designed  for  the  analysis  of  producer-gas,  water-gas, 
and  similar  mixtures.  It  is  a  simpler  form  of  apparatus  than 
those  formerly  described  by  Frankland  and  Ward  (J.  Chem.  Soc., 
1853,  vi.  p.  197),  and  later  on  modified  by  IVTLeod  (ibid.,  1869, 
xxii.  p.  313)  and  Thomas  (ibid.,  1879,  xxxv.  p.  213).  It  is 
usually  worked  with  mercury  as  confining  liquid. 

Fig.  57  shows  this  apparatus.  Its  essential  parts  are  the 
bulb  or  laboratory  vessel  A,  in  which  the  absorptions  and 
combustions  are  effected,  the  water-jacketed  measuring-tube  M 
and  the  levelling-tube  D.  The  upper  part  of  A  must  be 
sufficiently  wide  to  prevent  the  adherence  of  drops  of  liquid. 
The  measuring-tube  M  is  either  graduated  in  cubic  centimetres 
or  in  millimetres.  In  the  latter  case,  which  is  represented  in 
the  drawing,  the  tube  must  be  calibrated  by  mercury  in  the 
ordinary  manner.  Pressure  bulbs,  F  and  L,  supported  on 
wooden  blocks  z,  and  movable  in  the  notches  of  frame  H,  are 
attached  to  A  and  to  the  tube  V,  which  connects  the  measuring- 
tube  M  and  the  levelling-tube  D.  The  blocks  z  are  connected 
by  iron  strips  m  with  the  loops  w,  by  means  of  which  they  can 
be  easily  and  safely  put  in  any  of  the  notches  of  the  frames  H. 
The  tube  a,  placed  at  the  bottom  of  bulb  A,  is  connected  with 
F  by  a  thick  india-rubber  tube.  . 

Inside  bulb  A  is  the  combustion-tube^,  which  is  shown  on 
a  larger  scale  in  Fig.  58.  It  consists  of  a  nickel  tube,  in  which 
a  nickel  wire  v,  insulated  by  a  glass  tube,  is  fixed.  The  tube 


96  TECHNICAL  GAS-ANALYSIS 

and  the  wire  are  at  the  top  connected  by  a  platinum-wire  spiral. 
The  bottom  end  of  this  tube  projects  outside  the  bulb  A,  and 
the  wire  v  is  provided  with  a  screw  clamp,  for  connecting  it 
with  the  source  of  electricity.  In  order  to  keep  the  platinum 
wire  at  an  even  temperature,  and  thus  to  prevent  it  from  fusing 
by  excessive  heating,  an  adjustable  resistance  should  be  placed 
in  the  circuit  to  regulate  the  current.  Three  Grove 
cells  will  keep  the  spiral  red-hot  for  one  and  a 
half  to  two  minutes,  which  is  sufficiently  long  for  a 
combustion  to  be  completed.  If  the  platinum  wire 
turns  bright  red,  the  resistance  should  be  increased 
to  prevent  it  from  getting  still  hotter  and  ultimately 
fusing. 

The  tubes  attached  to  the  measuring-tube  M 
and  the  laboratory  vessel  A  are  connected  at  v 
by  rubber  tubing  and  brass  clips  (the  distance 
between  v  and  d  is  somewhat  greater  than  repre- 
sented in  the  figure)  ;  d  and  n  are  three-way  taps, 
and  h  a  simple  straight-bore  tap,  which  should  be 
FIG.  58.  from  12  to  15  mm.  thick  to  insure  its  keeping 

tight. 

To  introduce  the  gas  sample  tube  g  is  drawn  down  to  the 
bottom  of  bulb  A,  and  A,  M,  and  D  are  filled  with  mercury  by 
raising  bulbs  F  and  L;  the  taps  d  and  h  are  then  closed,  and 
the  gas  is  syphoned  into  A  through  the  three-way  tap  d,  by 
turning  it  so  as  to  connect  the  gas  supply  with  A.  If  the  gas 
is  to  be  drawn  from  a  sealed  bulb,  this  is  attached  to  the  rubber 
tube  connected  with  tap  d,  and  the  end  broken  inside  the 
tubing  ;  the  other  end  is  broken  off  under  mercury,  in  a  suitable 
containing  vessel,  and  the  gas  is  drawn  into  A  by  lowering  the 
pressure  bottle  F,  after  turning  tap  d  so  as  to  make  connection 
with  A.  Now  taps  d  and  h  are  turned  90°,  and,  by  raising  bulb 
F  and  lowering  L,  the  necessary  quantity  of  gas  is  forced  into 
M.  Any  excess  of  gas  or  any  liquid  remaining  in  A  is  removed 
by  opening  tap  d,  so  as  to  make  connection  with  the  outside  air. 
After  reading  the  exact  volume  of  the  gas  in  M,  0-3  to  0-5  c.c. 
of  potassium  hydroxide  solution  are  introduced  through  the 
funnel  t  into  A,  for  the  absorption  of  carbon  dioxide.  The  gas 
is  then  transferred  from  M  into  A,  and  after  the  absorption 
syphoned  back  to  a  mark  just  in  front  of  tap  d.  The  volume  of 


FISCHER'S  APPARATUS  97 

the  connecting  capillary  tube  up  to  this  mark  must  be  ascer- 
tained in  the  calibration  of  M,  and  allowed  for.  For  the 
absorption  of  oxygen,  01  c.c.  of  a  1:3  pyrogallol  solution  is 
similarly  introduced  into  A,  where  it  already  finds  the  necessary 
potash  solution,  and  the  volume  of  the  gas  now  remaining  is 
again  measured  in  M.  (In  ordinary  producer-gas,  etc.,  there  is 
frequently  no  oxygen  whatever,  so  that  the  volume  of  the  gas 
remains  unchanged  in  this  operation.) 

After  the  determination  of  CO2  and  O,  the  bulb  A  must 
be  thoroughly  cleaned  before  burning  the  hydrogen,  carbon 
monoxide,  and  methane,  because  otherwise  some  of  the  carbon 
dioxide  formed  by  this  operation  would  be  at  once  retained 
by  the  caustic  liquor  present.  For  this  purpose  A  is  washed 
out  two  or  three  times  with  10  to  20  c.c.  of  water,  which  is 
introduced  through  the  funnel  /,  and  expelled  through  the  tap 
d.  If  by  mistake  any  of  the  absorbent  has  got  beyond  d,  or 
into  tube  M  itself,  it  is  removed  by  first  clearing  the  air  out 
of  A,  syphoning  water  from  A  into  M,  and  then  drawing  back 
the  gas  and  liquid  into  A,  until  the  mercury  reaches  d\  the 
gas  is  then  syphoned  back  into  M,  and  the  wash-water  expelled 
as  before  through  d. 

The  combustion  of  hydrogen,  hydrocarbons,  and  carbon 
monoxide  is  effected  by  drawing  the  necessary  quantity  of 
air  or  oxygen  into  tube  M.  For  100  parts  producer-gas 
usually  1 20  parts  of  air;  for  100  semi-water  gas  150;  and  for 
100  water-gas  350  parts  of  air  is  sufficient.  If,  for  instance, 
M  holds  1 20  c.c.,  it  should  not  receive  more  than  50  c.c.  of 
producer-gas,  to  which  now  60  to  70  c.c.  air  is  added ;  and  in 
the  case  of  water-gas,  only  25  c.c.  of  it  may  be  used  with  about 
80  c.c.  of  air.  As  this  quantity  of  gas  is  too  small  for  accurate 
determinations,  it  is  better  in  the  case  of  water-gas  to  employ 
in  lieu  of  air  a  mixture  of  35  c.c.  of  air  and  25  c.c.  of  oxygen 
for  40  c.c.  of  water-gas.  It  is  preferable  to  burn  this  mixture 
in  successive  portions  of  about  30  c.c.  at  a  time,  rather  than 
altogether,  especially  if  the  worker  has  no  experience  with 
the  apparatus ;  also,  it  is  advisable  to  effect  the  combustion 
under  slightly  reduced  pressure. 

The  oxygen  can  be  generated  in  a  small  tube  of  the 
form  shown  in  Fig.  59.  About  2  g.  of  potassium  chlorate  are 
heated  in  this  tube,  which  is  attached  by  a  to  the  rubber 

G 


98  TECHNICAL  GAS-ANALYSIS 

connection  of  the  tap  d.  Fig.  57.  After  the  contained  air  has 
been  cleared  out  through  e,  which  is  placed  under  water,  the 
taps  d  and  n  are  opened  to  first  clear  out  the  capillary  tube 
with  oxygen  ;  n  is  then  closed  and  the  oxygen  introduced  into 
A  by  lowering  F. 

The  gaseous  mixture  is  again  allowed  to 
go  back  into  M,  and  once  more  over  the  hot 
platinum  wire  into  B,  and  is  ultimately 
measured  in  M,  thus  ascertaining  the  contrac- 
tion caused  by  the  combustion.  Now  the 
carbon  dioxide  formed  is  determined  in  the 
manner  mentioned  on  p.  96,  afterwards  the 
oxygen  in  excess,  and  thereby  all  the  figures 
FlG  are  obtained  for  calculating  CO2,  CO,  CH4, 

H,  O,  and  N. 

If  scientifically  accurate  results  are  to  be  obtained  with 
this  apparatus,  the  tubes  M  and  D  are  graduated  in  millimetres, 
and  readings  taken  of  the  barometer,  the  height  of  the  columns 
in  M  and  D,  and  the  temperature  of  the  water  in  the  jacket 
round  M,  at  each  observation  during  the  analysis.  The 
volumes  are  then  reduced  to  o°  and  1000  mm.  pressure  by 
the  formula : 


V   = 


-  b  -  e) 


iooo[i  +  0-00366/1' 


in  which  v  is  the  volume  of  gas  read  off,  B  the  height  of  the 
barometer  (reduced  to  o°),  b  the  difference  of  level  between 
M  and  D,  and  e  the  tension  of  aqueous  vapour  at  the 
temperature  t  of  the  experiment.  By  adjusting  the  columns 
of  mercury  in  M  and  D  to  the  same  level  after  each  determina- 
tion, the  correction  for  pressure  is  avoided  ;  the  correction  for 
temperature  is  only  required  in  cases  where  special  accuracy 
is  called  for,  since  the  changes  of  temperature  in  case  of  a 
water-jacketed  measuring-tube  are,  as  a  rule,  but  slight  during 
the  interval  of  an  analysis. 

The  calculation  of  the  proportion  of  hydrogen,  carbon 
monoxide,  and  methane  follows  from  the  volumetric  changes 
according  to  the  equations  : 


H2  +  O  =  H2O;  CO  +  O  =  CO 


2 


FISCHER'S  APPARATUS  99 


The  contraction  in   the   case   of  hydrogen  (w)  is  =  —  ;  in 

the  case  of  carbon  monoxide  (c)  =  -,  and  in  that  of  methane 

(;;/)  =  2  ;  both  carbon  monoxide  and  methane  in  combustion 
yield  their  own  volume  of  carbon  dioxide.  Taking  V  as  the 
total  volume  of  combustible  gases,  n  as  the  total  contraction, 
and  k  as  the  total  carbon  dioxide  formed,  the  resulting  equations 
are  : — 

V   =    w  +  c+m;   n  =  -3-w  +  —  c+  2m ;  k  =  c+m. 

Or, 

Hydrogen  (w)  =   V  -  k. 

Carbon  monoxide  (c]   =   —  k  +  V  -  —  n. 

3  3 

Methane  Cm)  =   J_£_v  +  —  «. 

3  3 

The  following  is  an  example  of  the  analysis  of  a  producer- 
gas. 

Volume  of  gas  taken,  60  c.c. 

After  absorption  of  carbon  dioxide,  56-1  ;  therefore  3-9  c.c. 
carbon  dioxide. 

After  addition  of  air,  116-1  ;  therefore  60  c.c.  air  containing 
47-4  c.c.  nitrogen  has  been  added. 

After  combustion,  101-2;  therefore^  =  14-9. 

After     absorption     of    carbon     dioxide,     87-6;     therefore 
k  =  13-6. 

After  absorption  of  oxygen,  857. 

Of  this   nitrogen,   47-4   added   as    air;   therefore   38-3  c.c. 
nitrogen  and  V  =  (56-1  -  38-3)  =    17-8. 

Hence : — 

Volume  of  hydrogen  =  17.8-13.6  =  4.2  c.c. 

„          carbon  monoxide  =     4.5  +  17.8-10  =  12.3  c.c. 
„          methane  =     9-1-17.8+10  =  1.3  c.c. 

and  the  composition  of  the  producer-gas  : — 

Carbon  dioxide  .            .        3-9  c.c.  or  6-5  per  cent. 

Hydrogen       .  "-.  .        4-2      „  7-0        „ 

Carbon  monoxide  .  .12-3      „  20-5        „ 

Methane         ,  .  .        1-3      „  2-2        „ 

Nitrogen         .  .  .»      38-8      »  63-3        ., 

60-0  c.c.  or  i oo-o  per  cent. 


100  TECHNICAL  GAS-ANALYSIS 


APPARATUS  OF  DREHSCHMIDT. 

In  this  apparatus  (described  in  Berl.  Ber.,  1888,  pp.  3242 
et  seq. ;  J.  Gasbelucht.^  1 889,  p.  3)  mercury  is  employed  as 
confining  liquid  ;  the  variations  of  temperature  and  pressure 
are  compensated  by  the  arrangement  proposed  by  Petterson 
(Z.  anal.  Chem.,  xxv.  p.  467),  already  mentioned  supra^  p.  21, 
and  also  employed  in  some  of  Hempel's  gas-analytical  apparatus. 
Drehschmidt  describes  his  apparatus  as  follows  : — 

The  tap  b  attached  to  the  top  of  the  burette  B  possesses  a 
peculiar  bore,  shown  in  the  enlarged  drawing  at  the  side,  which 
allows  of  connecting  B  with  the  capillary  tubes  attached  to  each 
side,  one  of  which  (that  which  is  turned  upwards)  leads  to  the 
differential  pressure  gauge  M ;  the  other  capillary  can  be 
connected  by  means  of  a  rubber  tube  with  a  pipette.  More- 
over, M  can  be  connected  by  the  tap  b  with  the  upright  tube  on 
that  tap,  and  thereby  with  the  air  outside.  C  is  the  compensat- 
ing tube ;  it  is  at  the  top  provided  with  the  tap  a,  the  peculiar 
bore  of  which  (visible  in  the  enlarged  side  figures)  enables  C 
and  M  either  to  communicate  with  each  other,  or  with  the 
outside  air,  or  to  be  both  shut.  The  pressure  gauge  M,  con- 
taining a  drop  of  coloured  liquid  (either  dilute  sulphuric  acid  or 
high-boiling  petroleum)  is  tightly  joined  by  rubber  tubes  with 
the  two  lateral,  vertically  turned-up  tubes  belonging  to  the  taps 
a  and  b.  C,  B,  and  M  are  held  by  the  clip  k.  At  the  bottom 
the  burette  B  is  continued  into  a  rubber  tube  with  the  screw 
clamp/,  followed  by  a  simple  tap  e.  From  the  latter  a  thick 
rubber  tube  leads  to  the  levelling  bulb  N,  filled  with  mercury. 
The  water  jacket  surrounding  B  and  C  contains  a  stirring 
arrangement,  consisting  of  a  copper  wire  with  a  suitably  cut-out 
plate,  which  is  moved  up  and  down  before  taking  readings 
in  order  to  equalise  the  temperature.  A  drop  of  water  is 
introduced  both  into  B  and  C,  so  that  the  enclosed  gases  are 
saturated  with  moisture. 

The  burette  B  is  provided  with  a  millimetre  scale,  600  mm. 
long,  and  its  contents  from  tap  b  down  to  the  lowest  point  of  the 
scale  is  put  =  100  vols.,  which  space  must  be  calibrated  with 
mercury,  so  that  the  space  value  corresponding  to  each  mark  of 
the  graduation  can  be  entered  into  a  table  to  be  used  for  all 
further  measurements.  For  this  and  all  further  readings  the 


DREHSCHMIDT'S 


reading-microscope   of  Schmidt   and    Haensch,    in    Berlin,   is 
recommended. 

In   order    to    measure   off  exactly    100   vols.,   the   gas    is 
aspirated  into  the  burette  a  little  beyond  the  end  of  the  scale, 


FIG.  60. 

and  is  then  connected  by  turning  tap  b  with  its  upper  and 
right-hand  side  tube.  But  raising  N,  the  mercury  is  forced  up 
nearly  to  the  mark  600 ;  then  shut  £,  stir  the  water  in  the 
jacket  round  C  and  B,  and  take  off  the  surplus  pressure  by  a 
brief  opening  of  b.  By  means  of  the  pinchcock  f  bring  the 
mercury  up  to  exactly  the  mark  600.  Remove  the  slight  over- 


TECHNICAL  GAS-ANALYSIS 

pressure  of  the  gas  by  a  momentary  opening  of  by  and  then 
turn  this  tap  so  that  B  communicates  with  M.  Proceed  in  the 
same  way  with  the  compensating  tube  C,  which  before  had 
been  in  communication  with  the  outside  air.  The  index  in  M, 
which  is  about  5  mm.  long,  now  takes  a  certain  position,  which 
must  be  re-established  for  all  future  readings. 

The  absorptions  are  carried  out  in  pipettes,  which  differ 
a  little  from  the  Hempel  pattern.  The  bulb  P  of  the  pipette 
has  at  the  top  a  horizontally  turned  capillary  with  the  capillary 
three-way  tap  c\  at  the  bottom  it  passes  over  into  a  wide 
glass  tube  with  an  ordinary  glass  tap  </,  which  is  connected 
by  a  rubber  tube  with  the  level  bulb  O.  The  pipette  is  filled 
with  mercury.  By  lowering  O,  a  certain  quantity  of  the 
absorbing  liquid  can  be  easily  and  quickly  introduced  by  the 
tailpiece  of  c,  and  can  be  removed  again  by  raising  O.  Only 
in  the  case  of  the  pipette  charged  with  fuming  oil  of  vitriol, 
which  is  entirely  filled  therewith,  O  is  permanently  connected 
with  P  by  a  glass  tube. 

The  burette  is  connected  with  any  one  of  the  pipettes  by 
a  short  rubber  tube  in  such  a  way  that  the  two  ends  of  the 
outlet  tubes  of  b  and  c  are  in  narrow  touch,  tap  c  being  turned 
in  such  manner  that  the  bulb  of  the  pipette,  filled  up  to  this 
tap  with  a  few  cubic  centimetres  of  the  reagent,  is  shut  off. 
In  order  to  drive  the  gas  into  the  pipette,  first  a  is  turned  so 
as  to  shut  off  C  against  M  and  against  the  outside  air ;  only 
then  the  burette  is  opened  towards  the  pipette,  and  by  raising 
N  the  mercury  is  driven  just  up  to  the  tap  b,  for  which  purpose 
after  shutting  e  the  screw  pinchcock  f  is  employed.  When  the 
absorption  of  the  gas  goes  on  but  slowly,  the  pipette  is  shut  off 
by  tap  cy  the  rubber  joint  is  taken  off,  the  pipette  is  vigorously 
shaken  and  again  connected  with  the  burette.  When  on 
retransporting  the  remaining  gas  into  the  retort  the  reagent 
has  risen  nearly  up  to  the  capillary  part  of  the  pipette,  tap  d 
is  shut  so  far  that  the  rising  can  take  place  but  slowly,  and  it 
is  entirely  shut  when  the  liquid  has  got  up  to  c.  Now  bulb  N 
is  raised  so  high  that  the  mercury  level  therein  is  at  the  same 
height  as  that  in  the  burette,  and  tap  c  is  closed.  If  now  a 
connection  is  established  between  B  and  M,  the  index  in  M 
is  shifted  a  little  ;  by  means  of  the  screw  clamp  f  it  is  brought 
back  again,  and  M  and  C  are  also  put  into  communication. 


PFEIFFER'S  APPARATUS  103 

In  consequence  of  this,  and  of  the  stirring  of  the  water  in  the 
water  jacket,  mostly  the  index  is  again  shifted.  It  is  brought 
into  its  original  place  by  means  of/,  and  the  reading  is  now 
taken. 

Combustions  of  gases  are  made  by  Drehschmidt's  platinum 
capillary  which  has  been  already  shown  supra,  p.  92,  Fig.  56, 
in  connection  with  the  Hempel  apparatus.  So  much  oxygen 
or  air  is  mixed  with  the  gaseous  remainder,  or  a  measured 
part  of  it,  that  there  is  an  excess  of  oxygen  present.  From  the 
contraction  and  the  carbon  dioxide  formed,  the  original  pro- 
portion of  hydrogen  and  methane  is  calculated  as  shown 
on  pp.  98  et  seq. 

Mathers  and  Lee  (Chem.  Eng.^  1913,  xvii.  p.  161)  modify 
the  Drehschmidt  capillary  by  filling  a  quartz  tube  with  pieces 
of  platinum  wire,  closing  both  ends  with  pieces  of  wire  netting, 
and  placing  the  tube  between  a  mercury  pipette  and  a  mercury 
burette.  The  burette  contains  the  gaseous  residue  and  the 
oxygen.  The  combustion  takes  three  minutes ;  the  results 
are  exact.  The  expansion  of  the  gas  in  heating  must  be 
allowed  for  by  taking  notice  of  the  temperature  in  reading  off 
the  volume,  and  of  the  volume  of  the  tube  in  which  a  little 
carbon  dioxide  remains  at  the  end. 

A  simple  form  of  gas-analysis  apparatus,  in  which  mercury 
is  used  as  the  confining  liquid,  has  been  described  by  W.  A. 
Bone  and  R.  V.  Wheeler,  in/.  Soc.  Chem.  Ind.,  1908,  xxvii.  p.  10. 

PFEIFFER'S  APPARATUS. 

This  apparatus  is  specially  intended  for  the  analysis  of 
coal-gas,  and  is  described  in  /.  Gasbeleuchl.,  1 899,  xlii.  p.  209 ; 
it  is  supplied  by  H.  Horold,  glass-blower,  Magdeburg. 

Since  the  errors  that  may  arise  in  the  estimation  of  carbon 
monoxide  by  cuprous  chloride  are  not  altogether  overcome 
by  using  a  second  absorption  pipette,  since  a  partial  absorption  of 
the  residual  gases  other  than  carbon  monoxide  may  possibly 
occur,  PfeifTer  is  of  opinion  that  it  is  both  simpler  and  more 
accurate  to  estimate  the  carbon  monoxide  by  explosion,  together 
with  the  determination  of  the  hydrogen  and  methane.  From 
his  experience  he  also  regards  it  as  preferable  to  oxidise  the 
hydrogen  and  methane  together,  rather  than  to  adopt  the 


104 


TECHNICAL  GAS-ANALYSIS 


method  of  fractional  combustion.  From  these  considerations 
the  course  of  analysis  adopted  consists  in  the  successive 
estimation  of  the  carbon  dioxide,  heavy  hydrocarbons,  benzene, 
ethylene,  oxygen,  by  absorption  methods,  and  the  combustion 
of  hydrogen,  carbon  monoxide,  and  methane  by  explosion  in 
one  operation,  as  described  in  connection  with  F.  Fischer's 
apparatus  (supra,  p.  95).  Thus  the  lengthy  and  not  very  reliable 
absorption  of  carbon  monoxide,  as  well  as  the  fractional  com- 


FIG.  61. 


FIG.  62. 


bustion  of  hydrogen  and  methane  are  done  away  with.  By 
estimating  the  carbon  dioxide  formed,  the  total  contraction 
and  the  residual  nitrogen,  the  necessary  data  for  calculation  on 
the  lines  described  on  pp.  98  and  99  are  obtained.  A  complete 
analysis  of  coal-gas  can  be  carried  out  by  this  method  in  three- 
quarters  of  an  hour,  which  is  of  great  advantage  for  the  accuracy 
of  the  results.  Since  the  heavy  hydrocarbons  present  in  the 
form  of  vapour  and  of  gas  are  separately  estimated,  the  analysis 
permits  also  of  calculating  the  illuminating  value  of  the  gas. 

The  apparatus  consists  of  the  burette  and  levelling  flask, 
Fig.  61,  two  or  three  absorption  pipettes,  Fig.  62,  a  phosphorus 
pipette,  and  an  explosion  pipette,  Fig.  63. 


PFEIFFER'S  APPARATUS 


105 


The  burette  B  is  provided  with  a  stopcock  b  and  funnel, 
and  is  attached  to  the  pipette  P  as  shown ;  its  capacity  is  100 
c.c. ;  its  lower  end  is  connected  by  the  rubber  tube  S  with  the 
levelling  bottle  N,  holding  300  c.c.  The  confining  liquid  is 
water,  acidified  with  0-5  per  cent,  of  sulphuric  acid,  which  addi- 
tion prevents  the  absorption  of  carbon  dioxide,  and  takes  up  am- 
monia vapour  after  the  absorption  of  the  hydrocarbon  vapours. 

An  improved  form  of  burette,  designed  by  PfeifTer  specially 
for  the  analysis  of  coal-gas,  is  shown  in  Fig.  64,  and  as  arranged 


FIG.  63. 


FIG.  64. 


for  the  explosion  ot  the  combustible  gases  in  Fig.  65.  The 
bulb  R  at  the  top  of  this  burette  is  connected  by  a  narrow  tube 
to  the  lower  bulb ;  a  mark  m,  made  on  the  connecting  tube, 
serves  for  measuring  off  the  gas  residue  taken  for  combustion. 
The  total  capacity  of  the  burette  between  the  two  stopcocks  is 
sufficient  to  admit  of  employing  the  volume  of  air  requisite  for 
the  combustion  of  the  gas  residue.  The  relative  capacity  of 
the  two  spaces,  for  coal-gas  and  for  carburetted  water-gas, 
should  be  about  I  :  5.  The  exact  capacity  of  the  burette  up  to 
m  (=  R),  also  the  total  capacity,  J,  and  the  volume  of  nitrogen 
contained  in  J  when  filled  with  air  =  Nx,  are  marked  on  the 
burette  by  etching,  as  shown  in  Fig.  64.  Hence  this  burette 
permits  the  exact  measurement  of  the  gas  residue  and  of  the 
air  which  are  successively  passed  into  the  explosion  pipette. 


106 


TECHNICAL  GAS-ANALYSIS 


Owing  to  the  form  given  to  this  burette,  that  part  of  it  which 
serves  for  the  measurements  can  be  kept  narrow  enough  to  be 
provided  with  a  division  marking  01  mm.  The  zero  point  is 
just  above  bulb  R,  below  the  capillary,  because  the  latter  is 
filled  with  water  after  re-conducting  the  gaseous  remainders  into 
the  burette.  Only  in  the  first  measurement  of  the  gas  this  is 
not  the  case,  wherefore  in  this  the  contents  of  this  capillary,  say 


FIG.  65. 

for  example  02  c.c.,  must   be  taken  into  account,  as  will  be 
explained  infrfr. 

In  lieu  of  the  Hempel  absorption  pipette,  Pfeiffer  employs 
the  modified  form  shown  in  Fig.  62,  which  permits  of  the 
replacement  of  the  gas  in  the  capillary  connecting  tube  by 
means  of  water.  The  figure  shows  the  capillary  side-tube  at  c, 
which  is  connected  with  the  burette ;  by  altering  the  position 
of  the  stopcock  /,  in  the  manner  which  can  be  readily  under- 
stood from  the  diagram,  water  may  be  run  from  the  funnel  t 
into  the  capillary  cy  and  the  air  expelled  before  connecting  with 


PFEIFFER'S  APPARATUS  107 

the  burette;  and  when  drawing  the  gas  back  to  the  burette 
after  absorption,  the  absorbing  liquid  is  allowed  to  rise  only  to 
the  stopcock  / ;  after  which,  by  turning  the  latter  through  an 
angle  of  90°,  water  is  run  from  the  funnel  t  into  the  capillary  c, 
the  gas  remaining  in  which  is  thus  forced  into  the  burette; 
this  operation  is  carried  out  before  each  reading.  In  place  of 
the  wooden  or  metal  stand  used  by  Hempel,  the  tube  is  bedded 
in  a  sheet-metal  case  by  means  of  paraffin  wax  or  plaster-of- 
Paris. 

To  take  the  sample  of  the  gas,  the  burette  B  is  first  filled 
completely  with  water  by  raising  the  levelling  vessel  N,  and 
opening  the  stopcocks  b±  and  b  (Fig.  61),  and  the  sample  is  then 
drawn  in  by  lowering  N  in  the  usual  manner,  until  the  volume 
of  gas  is  a  little  below  the  zero  mark ;  the  stopcocks  are  then 
closed,  and  N  is  again  raised.  To  measure  off  exactly  100  c.c., 
the  lower  stopcock  b^  is  carefully  opened,  and  the  water  allowed 
to  rise  to  the  true  zero ;  the  upper  stopcock  b  is  then 
momentarily  opened,  and  the  volume  checked  in  the  usual 
manner  with  the  levelling  bottle  N.  In  the  first  reading  the 
zero  lies  as  much  below  the  zero  mark  as  is  equivalent  to  the 
content  of  the  capillary  at  3,  since  the  latter  is  filled  with  water 
in  the  subsequent  measurements,  and  the  100  c.c.  graduation  is 
at  the  lower  end  of  the  capillary.  This  correction  (generally 
0-2  c.c.)  is  therefore  determined  once  for  all  as  follows : — 

Air  is  introduced  into  the  burette  to  about  the  division  90, 
then  water  until  the  capillary  at  b  is  filled,  the  stopcocks 
are  closed,  and  the  reading  taken  after  two  minutes  ;  meanwhile 
the  water  is  completely  removed  from  the  capillary  tube  of  the 
stopcock,  the  water  then  run  out  of  the  capillary  into  the  burette 
and  another  reading  taken ;  the  difference  between  the  two 
readings  gives  the  capacity  of  the  capillary.  It  is  advantageous 
to  use  a  meniscus  screen,  such  as  that  of  Gb'ckel  (p.  35)  in 
taking  the  readings,  so  as  to  avoid  parallax  errors. 

The  single  constituents  of  the  gas  are  estimated  as  follows  : — 

Carbon  Dioxide. — The  pipette,  Fig.  62,  is  filled  up  to  the  top 
with  potassium  hydroxide  solution,  and  is  connected  with  the 
burette  as  shown  in  Fig.  61.  The  stopcocks  of  both  the  burette 
and  the  pipette  are  turned  to  the  position  in  which  the  two 
funnels  communicate  with  each  other;  water  is  poured  into  one 
of  them  to  expel  the  air  from  the  connection  b-s-p ;  the 


108  TECHNICAL  GAS-ANALYSIS 

stopcocks  of  the  burette  and  of  the  pipette  are  turned  through 
1 80°,  and  the  gas  is  transferred  from  the  burette  into  the  pipette. 
While  it  is  passing  over,  the  contents  of  the  pipette  are  shaken 
for  a  moment,  so  as  to  mix  the  water  from  the  capillary 
connections  with  the  alkali.  As  soon  as  the  water  reaches  the 
stopcock/,  the  burette  stopcock  £  is  closed;  the  absorption  is 
complete  in  one  minute.  The  gas  is  then  syphoned  back  into 
the  burette  by  lowering  the  bottle  N  until  the  alkali  reaches 
the  stopcock  /  of  the  pipette,  which  is  then  turned  through 
1 80°,  and  the  gas  in  the  capillary /-.$•-£  is  washed  out  as  before 
by  means  of  the  water  in  the  pipette  funnel.  The  burette 
stopcock  b  is  then  closed  and  the  reading  taken  as  usual,  after 
allowing  to  stand  for  one  minute. 

Benzene  Vapour. — This  is  absorbed  with  ammoniacal  nickel 
cyanide  solution  ;  after  shaking  for  three  minutes  (it  is  preferable 
to  facilitate  the  shaking  in  this  case  by  detaching  the  pipette), 
the  residual  gas  is  returned  again  to  the  burette,  where  the 
absorption  of  the  ammonia  vapours  is  effected  by  the  acidulated 
water  used  as  the  confining  liquid.  As  a  check,  about  0-5  c.c.  of 
fresh  acidulated  water  is  introduced  into  the  burette  from  the 
pipette  funnel. 

The  ammoniacal  solution  of  nickel  cyanide,  recommended 
for  the  estimation  of  benzene  vapour  by  Dennis  and  McCarthy, 
J.  Amer.  Chem.  Soc.,  1908,  xxx.  p.  233,  is  prepared  as  follows: — 
A  solution  of  25  g.  potassium  cyanide  in  25  c.c.  of  water  is 
added  to  a  solution  of  50  g.  of  crystallised  nickel  sulphate  in 
75  c.c.  of  water,  125  c.c.  of  ammonia  (sp.  gr.  0-91)  added,  the 
whole  cooled  to  o°,  and  poured  off  from  the  separated  potassium 
sulphate;  a  solution  of  18  g.  of  citric  acid  in  10  c.c.  of  water  is 
then  added,  the  mixture  again  cooled  to  o°  for  ten  minutes, 
decanted  from  the  potassium  sulphate  crystals,  and  a  few  drops  of 
benzene  then  added  and  shaken  till  combination  takes  place,  as 
the  solution  is  much  more  active  after  it  has  absorbed  some 
benzene.  This  solution  has  no  action  on  ethylene  or  on  carbon 
monoxide;  the  former  may  be  estimated  by  absorption  with 
bromine  or  fuming  sulphuric  acid  after  the  removal  of  the 
benzene.  The  small  quantities  of  benzene  homologues  present 
would  not  be  absorbed  by  the  ammoniacal  nickel  cyanide ;  but 
their  amount  rarely  exceeds  o  i  percent.  Some  contend  that 
it  is  difficult  to  remove  the  ammonia  from  the  remaining  gas, 


PFEIFFER'S  APPARATUS  109 

but  Pfeiffer,as  he  states  in  Lunge-BerPs  Chem.  Techn.  Unt.  Meth., 
iii.  p.  238,  did  not  confirm  this. 

Ethylene  (or  total  heavy  hydrocarbons,  if  the  separate 
estimation  of  benzene  vapour  is  not  required)  is  absorbed  by 
vigorously  shaking  for  three  minutes  with  bromine  water.  The 
bromine  vapours  are  subsequently  removed  by  forcing  the 
gaseous  remainder  into  the  potash  pipette,  manipulating  just  in 
the  same  way  as  if  the  gas  had  to  be  transferred  into  the 
burette.  This  is  done  by  sucking  at  the  open  end  of  the  potash 
pipette  by  means  of  a  rubber  tube.  Then  this  pipette  is 
connected  with  the  burette,  and  the  reading  made. 

Oxygen  is  estimated  in  the  phosphorus  pipette  (Fig.  51, 
p.  85).  The  capillary  space  between  the  pipette  and  burette 
is  cleared,  by  forcing  the  water  from  the  pipette  into  the 
burette  funnel  by  attaching  a  piece  of  rubber  tubing  to  the 
open  end  of  the  pipette  and  blowing. 

Carbon  Monoxide,  Hydrogen,  Methane,  and  Nitrogen. — The 
explosion  pipette,  Fig.  63,  is  used  for  the  estimation  of  these 
gases.  In  the  analysis  of  coal-gas  from  20  to  22  c.c.  of  the  gas 
left  after  absorption,  which  requires  about  five  volumes  of  air 
for  combustion,  are  first  measured  off  in  the  burette,  allowing 
the  excess  to  escape ;  since,  in  doing  so,  the  capillary  at  b  is 
freed  from  water,  its  capacity,  as  determined,  must  be  added  to 
the  reading.  The  burette  and  explosion  pipette  are  then  con- 
nected, the  air  in  the  connecting  capillaries  displaced  as  in  the 
case  of  the  phosphorus  pipette,  and  the  gas  passed  over.  The 
explosion  pipette  is  then  disconnected  and  the  burette  filled 
with  air.  The  air  is  then  transferred  to  the  explosion  pipette, 
the  water  allowed  to  rise  as  far  as  the  bulb  of  the  pipette,  the 
stopcock  a  then  closed,  and  the  small  quantity  of  water  remaining 
in  the  explosion  chamber  A  withdrawn  into  the  reservoir  B, 
so  that  only  the  V-snaPed  connection  remains  filled  with  water; 
the  stopcock  b  is  then  closed.  An  electric  spark  is  then  passed 
through  the  mixture  in  the  usual  manner,  the  pipette  stopcock 
carefully  opened  so  that  the  enclosed  water  comes  back  into  the 
explosion  chamber  quickly,  and  a  little  oxygen  passed  back 
into  the  burette.  The  carbon  dioxide  formed  in  the  combustion 
is  then  absorbed  by  potassium  hydroxide,  and  the  excess  of 
oxygen  by  phosphorus,  whereby  a  direct  measurement  of  the 
total  nitrogen,  inclusive  of  that  added  as  air,  is  obtained. 


110 


TECHNICAL  GAS-ANALYSIS 


Calculation  of  the  Results. — This  takes  place   according   to 
the  following  equations  : — 

H   =   V-CO2. 
CO   =   C02  +  V-  — C. 

CH4  =  —  C-V. 

Here    V    signifies    the    combustible    gases,  C  the   total   con- 
traction after  absorption  with  alkali. 

The  sequence  of  the  separate  readings  and  the  resulting  data 
are  shown  by  the  following  example  : — 


Readings. 

Data. 

In  residue  B. 

In  100  parts 
of  gas. 

A.  ABSORPTION. 

Initial  reading 

1  00-0 

... 

... 

After  absorption  with  alkali  . 

98-3 

... 

... 

CO2  =  1-70 

After  absorption  with  nickel 

solution     .... 

97-27 

... 

C6H6=  1.03 

After  absorption  with  bromine 
After  absorption   with  phos- 

94.48 

C2H4=  2-79 

phorus        .... 

93-7 

... 

... 

0  =  0-73 

B.  EXPLOSION. 

Gas  residue  taken  (R) 

22-4 

V-  21-55 

H  =  13-75 

H  =  57.5i 

Air  added  (J) 

113-1 

CH4  =    6-05 

CH4  =  25.3i 

Reading  after  explosion 
Reading      after      absorption 

101-9 

C  =  41-40 

CO   =    1-75 

00  =  73-72 

with  alkali 

9*-t 

CO2  =    7«8o 

... 

... 

Reading      after      absorption 

with  phosphorus 

90-25 

N!  =  89-40 

N    =    0-85 

N   =  3-56 

VARIOUS   APPARATUS   FOR  TECHNICAL 
GAS-ANALYSIS. 

We   here   mention   only   some   of   the   recently   described 
apparatus,  modifying  those  described  supra .' — 

Lomschakow  (Ger.  P.  251734). 
Gockel  (/.  Gasbeleucht.,  1912,  p.  1057). 

Taplay  (/.  Gas  Lighting^  cxviii.  pp.  217  and  285  ;  cxxii.  pp. 
870  and  933). 

Burrell  (/.  Inst.  Eng.  Client.,  iv.  pp.  297  and  1445). 
Eckardt  (Ger.  Ps.  241686  and  242315). 
Egnell  (B.  P.  29211  of  1911). 


VARIOUS  APPARATUS  111 

Agraz  (Z.  anal.  Chem.,  1913,  p.  418  ;  Abstr.  Amer.  Chem.  Soc., 

1913,  p.  3049). 

Liese  (B.  Ps.  27467  of  191 1  ;  23656  of  1912). 
Einer  lohnson  (Amer.  P.  1074795). 
Hayes  (Amer.  P.  1077342). 
Kleine  (Ger.  P.  190240). 
Siemens  and  Halske  (Fr.  P.  458916). 

Arndt  (B.  P.  15019  of  1912  ;  Ger.  Ps.  241075,  242540,  242650). 
Matzerath  (Ger.  P.  Appl.  M.  59308). 


APPARATUS  FOR  THE  RAPID   AND   CONTINUOUS 
ANALYSIS  OF  GASES. 

During  recent  years  various  methods  and  many  apparatus 
for  a  rapid  and  continuous  testing  of  gaseous  mixtures  have 
come  into  use.  Most  of  these  are  destined  for  the  examination 
of  fire-gases,  or  smoke-gases,  or  coal-gas,  and  we  shall  mention 
them  later  on  in  treating  of  these  gases. 

In  this  place  we  only  mention  the  gas-analysis  apparatus 
constructed  by  Simmance,  Abady,  &  Wood,  East  Sheen, 
Surrey  (B.  P.  11664  of  1912),  Ph.  Eyer  (Ger.  P.  256218). 

Harger  (B.  P.  9623  of  1912;  Abstr.  Amer.  Chem.  Soc.,  1912, 

P-  3255). 

A.  Schmid  (B.  P.  25046  of  1912). 

Eynon  (Amer.  P.  1052412  of  1913). 

Hiifner  (B.  P.  11679  of  1912  ;  Ger.  P.  247335). 

Woodroffe  and  Boultbee  (B.  P.  5039  of  1912). 

L.  Sanders,  Assignor  to  the  Sarco  Fuel  Saving  and 
Engineering  Company,  New  York  (B.  P.  1683  of  191 1  ;  Amer.  P. 
1055420). 

Burrell  and  Seibert  (Bureau  of  Mines  Tech.  Pap.,  1913, 
vol.  31,  p.  i). 

Davidson  (described  by  Balcon  in  J.  Gas  Lighting,  1913, 
p.  102). 

Bone  and  Wheeler  (J.  Soc.  Chem.  Ind.,  1908,  p.  10). 

Than  (Z.  angew  Chem.,  1912,  ii.  p.  90). 

Cross  (Ger.  P.  243603). 

Hartung  (Ger.  P.  244859). 

Knoll  (Ger.  P.  248318). 

Levy  (B.  P.  12841  of  1911). 


112  TECHNICAL  GAS-ANALYSIS 

Heckmann  (Ger.  P.  252538). 

Arndt  (Ger.  P.  242540). 

Martens  (B.  P.   11851  of  1911;  Amer.  P.  1060996;  Ger.  P. 

234983). 

Boulton  (B.  Ps.  5601  and  16300  of  1912  ;  Amer.  P.  1074795). 


VARIOUS   METHODS    EMPLOYED    IN    TECHNICAL 
GAS-ANALYSIS. 

I.  ESTIMATION  OF  SOLID  AND  LIQUID  ADMIXTURES  (SOOT, 
DUST,  ETC.)  IN  GASES. 

The  gases  to  be  examined  in  the  practice  of  chemical 
operations  frequently  contain  solid  or  liquid  substances, 
mechanically  carried  along,  which  cannot  always  be  entirely 
retained  by  rest,  filtration,  or  washing.  The  liquid  admixtures 
are  always  accompanied  by  vapours  of  the  same  substance, 
if  this  is  volatile. 

Although  in  most  cases  the  presence  of  such  solids  or  liquids 
in  a  gas  does  not  sensibly  influence  its  volume,  and  hence  has 
no  influence  on  the  results  of  gas-volumetric  analysis,  it  is 
frequently  desirable  for  general  purposes  to  remove  these 
impurities,  and  therefore  methods  are  required  for  estimating 
their  quantity.  This  is  usually  done  when  taking  the  samples 
of  the  gas  for  its  analysis.  Of  course  we  must  know  the 
quantity  of  gas  in  question,  and  since  for  the  purpose  of 
estimating  those  impurities  comparatively  large  quantities  of 
gas  must  be  employed,  its  quantity  is  generally  measured  by 
a  gas-meter,  or  else  by  an  aspirator  worked  by  outflowing 
water.  The  meter  or  aspirator  is  always  placed  behind  the 
gas-analytical  apparatus. 

Solid  admixtures  (Cf.  Lunge-Keane's  Techn.  Methods,  i. 
pp.  899  et  seq.)  in  the  case  of  smoke-gases,  producer-gases, 
and  analogous  cases  consist  partly  of  soot,  partly  of  minute 
particles  of  minerals,  metals,  coal,  etc.  In  the  flue-dust  from 
metallurgical  operations  are  found  the  oxides,  sulphides, 
sulphates,  chlorides,  etc.,  of  various  metals. 

The  quantity  of  dust  contained  in  a  gas  may  vary  between 


SOLID  ADMIXTURES  113 

great  limits.     Thus  Fodor  found  in  the  street  air  of  Budapest, 
1 5  ft.  above  the  street  level,  on  the  average  : 

In  winter  .  .  0-00024  g-  dust  per  cubic  metre 

„  spring  .  .  0-00035               „            „ 

„  summer  .  .  0-00055              „            „ 

„  autumn  .  .  0-00043              »            „ 

Tissandier  found  in  the  air  of  Paris,  after  a  week's  dry 
weather  0-0230,  after  heavy  rain  0-0060  g.  dust  per  cubic  metre. 
Hesse  found  in  a  cubic  metre  of  air  from  a  living-room  and 
nursery  0-0016  g.,  from  the  rag-picking  shed  of  a  paper  work 
0-0229  g.,  from  the  cleaning-room  of  a  foundry  o-iooo  g.  dust. 
Stapff  found  in  a  cubic  metre  of  air  from  the  St  Gothard 
Tunnel,  during  the  time  it  was  constructed,  1-900  g.  dust; 
Theisen  in  the  same,  before  washing  the  air  3-340  g.,  after 
washing  o-oio  g.  dust.  Scheurer-Kestner  found  in  chimney- 
gases  from  a  coal  fire,  when  strongly  firing  0-2209,  when 
damping  the  fire  0-9649  g.  carbon  as  soot.  Krause  found  in 
I  cbm.  of  air  from  a  match  factory  0-004  to  0-005  g-  phosphorus. 

Large  quantities  of  air  must  be  employed  for  estimating 
the  dust,  if  not  merely  its  quantity  is  to  be  ascertained,  but 
a  microscopical  and  chemical  examination  is  to  be  made  for 
determining  its  hygienic  properties,  or  its  value,  or  its 
inflammability.  The  latter  exerts  great  influence  in  the  case 
of  explosions  in  coal  pits  and  flour  mills. 

The  retention  of  solid  substances  mixed  with  a  gas  in  the 
shape  of  dust  is  performed  by  filtration.  Even  very  small 
particles,  down  to  about  0-0002  mm.  diameter,  such  as  they 
occur,  e.g.  in  coal  smoke,  can  be  retained  by  employing  a 
suitable  filtering  medium,  a  sufficient  filtering  surface,  and 
a  not  over  rapid  current  of  gas.  Carded  cotton-wool  is  very 
efficient,  but  is  not  adapted  to  filtering  air  in  the  presence  of 
acid  gases.  In  this  case  gun-cotton  or  soft,  curly  glass-wool 
is  employed.  This  material  is  placed  in  a  so-called  calcium 
chloride  tube,  and  is  dried  by  exposing  the  tube  in  an  air-  or 
water-bath  at  100°  to  a  current  of  dry  air,  until  the  weight 
remains  constant.  This  tube  is  interposed  between  the  place  the 
air  of  which  is  to  be  examined  and  an  aspirator  or  gas-meter. 
A  suitable  volume  of  gas,  say  about  I  cbm.  per  twenty-four 
hours,  is  drawn  through  the  tube,  which  is  then  dried  at  100°, 

H 


114  TECHNICAL  GAS-ANALYSIS 

and  the  increase  of  weight  is  ascertained.  If  the  retained 
dust,  which  is  principally  found  at  the  entrance  end,  is  to 
be  further  examined,  this  can  be  done  by  the  microscope 
and  by  the  ordinary  chemical  methods. 

The  filtration  of  gases  through  filtering  paper  has  been 
employed  by  Moeller,  and  has  been  worked  out  more  fully 
by  Rubner  and  Renk  (Arb.  aus  d.  hygien.  Inst.  Dresden^  1907 ; 
Hempel's  Gasanal.  Methoden,  4th  ed.,  p.  123). 

Friese  recommends  for  this  purpose  the  "  blue-band  "  paper 
of  Schleicher  and  Schull,  ordinary  filtering  paper  not  being 
sufficient  for  retaining  all  descriptions  of  dust. 

O.  Brunck  employs  for  collecting  the  dust  from  the  air  of 
coal  pits  liable  to  contain  fire-damp,  filtering  tubes  provided 
with  ground-on  glass  caps,  which  admit  of  weighing  the  dust 
with  its  natural  moisture.  These  tubes  are  carried  about  in 
boxes  lined  with  cork  slabs,  of  such  size  that  the  caps  cannot 
fall  off. 

Martens  (Stahl  u.  Eisen,  1903,  xxiii.  p.  735)  employs  for 
the  retention  of  dust,  filtering  paper  extended  between  two 
metallic  funnels  and  protected  against  tearing  by  a  metal 
sieve  placed  on  it. 

Simon  (ibid.,  1905,  xxv.  p.  1069)  proposes  for  this  purpose 
Soxhlet's  ether-extraction  capsules,  dried  before  and  after 
use  at  105°. 

Schroeder  (Z.  fiir  chem.  Apparatenkunde,  1907,  ii.  p.  458) 
first  retains  the  coarse  dust  in  two  vertically  placed  brass  tubes, 
nickel-coated  inside,  the  second  of  which  contains  a  cross  wall ; 
the  fine  dust  is  afterwards  retained  by  a  glass-wool  filter. 

Kershaw  (Ranch  und  Staub,  1913,  p.  193)  describes  some 
methods  for  estimating  and  registering  the  dust  and  soot  in  air. 

The  following  class  of  apparatus  is  especially  intended  for 
ascertaining  the  quantity  of  soot  in  furnace-gases.  Usually 
a  known  volume  of  these  gases  is  drawn  through  a  tube  of 
refractory  glass,  containing  a  layer  of  asbestos,  20  cm.  long. 
The  soot  retained  here  is  afterwards  burned  in  a  current  of 
oxygen,  and  the  carbon  dioxide  absorbed  in  potash  bulbs,  in 
the  same  way  as  in  elementary  organic  analysis,  of  course 
interposing  a  calcium  chloride  tube  in  front  of  the  potash  bulbs. 

Several  methods  have  been  described  for  the  colorimetric 
estimation  of  sooty  matters  in  chimney -gases,  etc.  Thus 


LIQUID  ADMIXTURES  115 

Fritzsche  (Z.  Verein.  deutsch.  Ingen.,  1897,  p.  885)  describes 
a  test,  founded  on  the  more  or  less  pronounced  grey  colour 
of  a  filtering  medium,  consisting  of  cellulose  fibre,  which  is 
afterwards  shaken  up  with  a  certain  volume  of  water,  and 
compared  with  the  colour  of  paper  tinted  by  Indian  ink. 

H.  Wislicenus  (Z.  angew.  Chem.,  1901,  p.  689)  exposes  the 
air  of  forests,  suspected  of  being  contaminated  by  sooty  gases, 
to  frames  covered  with  thin  calico,  and  compares  the  degree  of 
blackening  produced  after  a  certain  time  with  that  of  pure  air. 

Silbermann  (Ger.  P.  179145;  Z.  fur  chem.  Apparatenkunde, 
1907,  ii.  p.  1907)  describes  an  apparatus,  in  which  the  degree 
of  blackening  by  sooty  gases  is  ascertained  by  the  assistance 
of  a  selenium  cell. 

Strong  (B.  P.  20199  of  1912)  describes  an  apparatus  for 
detecting  suspended  matter  in  gases,  especially  those  passed 
between  insulated  electrodes,  by  the  change  in  the  current. 

Phillips  (Trans.  %th  Intern.  Congr.  Appl.  Chem.,  xxv.  711; 
Abstr.  Amer.  Chem.  Soc.  1913,  p.  2467)  describes  a  special  filter 
for  this  purpose. 

Liquid  admixtures  in  gases  occur  mostly  in  the  shape  of 
vapour,  especially  if  the  sample  is  taken  in  the  hot  state,  and 
they  would  then  be  estimated  by  the  processes  for  estimating 
gaseous  substances,  described  elsewhere.  In  cooling,  the  liquid 
may  be  partially  condensed,  but  this  condensation  is  never 
sufficiently  complete  to  admit  of  a  quantitative  estimation  of 
the  substance  in  question ;  it  should  be  always  combined  with 
an  absorbing  or  washing  process,  in  order  to  ascertain  the  total 
quantity  of  the  impurity. 

Water  (moisture)  is  estimated  by  absorption  in  a  weighed 
calcium  chloride  tube.  If  the  gas  contains  ammonia  it  is 
preferable  to  employ  the  drying  agent  employed  by  Stas,  and 
later  on  by  C.  Frenzel  (Z.  Elektrochem.,  1900,  p.  486),  which  is 
prepared  by  heating  a  mixture  of  3  parts  of  finely  divided 
copper  and  i  part  potassium  chlorate  in  an  iron  crucible  to  a 
strong  red  heat.  The  estimation  of  moisture  by  physical 
methods  ("  hygrometry  ")  does  not  enter  into  the  scope  of  this 
treatise. 

Mercury  (of  which  Tanda  found  0-00875  g.  per  cubic  metre 
in  the  principal  chimney  of  the  Idria  quicksilver  works) 
is  estimated  by  interposing  a  weighed  tube,  filled  with  gold 


116  TECHNICAL  GAS- ANALYSIS 

foil,  and  reweighing  after  the  passage  of  the  gas.  Kunkel's 
method  will  be  described  later  on. 

Sulphuric  acid,  occurring  as  such  or  as  sulphuric  trioxide, 
together  with  sulphur  dioxide  in  gases  from  roasting  ores,  etc., 
is  found  by  estimating  the  total  acids  (vide  infra)  and  sub- 
tracting the  SO2  found  by  titration  in  another  sample. 

The  estimation  of  a  number  of  other  liquids  which  occur 
in  gases,  mostly  in  the  shape  of  vapour,  will  be  described  later 
on  when  treating  separately  of  these  substances. 

II.  ESTIMATION  OF  GASES  BY  ABSORPTION. 

A—  BY  GAS-VOLUMETRIC  METHODS. 

The  gas-volumetric  estimation  of  a  gas  by  absorption  is  an 
estimation  by  difference.  It  is  performed  by  taking  out  of  a 
known  volume  of  gas  the  absorbable  gaseous  constituent  by 
means  of  a  suitable  reagent,  measuring  the  residual  gas,  and 
subtracting  its  volume  from  the  original  volume  of  gas. 

In  previous  chapters  we  have  described  numerous  apparatus 
for  this  purpose,  such  as  the  absorbing  parts  of  the  Orsat 
apparatus  and  its  various  modifications  (p.  66),  of  Dennis 
(p.  76),  of  Hempel  (p.  82),  of  Drehschmidt  (p.  100),  of  Pfeiffer 
(p.  103),  and  we  shall  describe  some  others  later  on.  A  new 
apparatus  for  this  purpose  is  described  in  the  Ger.  P.  270088  of 
the  Dragerwerk. 

In  this  place  we  shall  treat  of  the  absorbing  agents ',  reserving, 
however,  for  a  later  chapter  the  description  of  such  absorbents 
as  are  used  only  in  special  cases.  In  preceding  chapters  we 
have  already  had  frequent  occasion  to  speak  of  these  agents, 
but  in  this  place  we  shall  describe  them  generally. 

General  Remarks.  —  The  absorbing  agents  are  mostly 
employed  in  the  form  of  solutions,  frequently  in  a  con- 
centrated state,  especially  where  they  have  to  be  used  over 
and  over  again.  As  a  rule,  it  is  preferable  to  use  the  same 
absorbing  liquid  continually,  nearly  up  to  exhaustion,  in  order  to 
diminish  the  error  caused  by  the  mechanical  solubility  of  gases 
not  intended  to  be  retained,  and  not  absorbed  by  a  chemical 
reaction.  When  employing  a  freshly  prepared  absorbing  liquid, 
this  mechanical  solution  may  take  place  to  quite  a  sensible 
extent,  leading  to  incorrectly  high  results  for  the  gas  to  be 


ABSORBENTS  FOR  CARBON  DIOXIDE  117 

chemically  absorbed  on  purpose  ;  this  error  does  not  take  place 
when  the  liquid  has  been  saturated  with  the  mechanically 
dissolved  gases. 

It  must  not  be  overlooked  that  the  absorbing  agents 
mechanically  dissolve  some  of  the  gases  supposed  to  pass 
quite  unchanged  through  them.  This  causes,  however,  too 
slight  a  fault  to  be  worth  noticing  in  technical  gas-analysis, 
where  consecutive  analyses  are  made  by  means  of  the  same 
apparatus  used  for  many  single  analyses. 

(a)  Absorbents  for  Carbon  Dioxide. 

The  general  absorbent  for  this  purpose  is  a  solution  of 
potassium  hydroxide,  which  retains  the  CO2  easily  and  rapidly. 
The  ordinary  solution  is  prepared  by  dissolving  250  g.  of  good 
commercial  caustic  potash,  which  need  not  be  purified  by 
means  of  alcohol,  in  water  and  diluting  the  solution  to  800  c.c. 
One  c.c.  of  this  liquor  contains  about  0-21  g.  real  KOH,  and 
consequently  absorbs  0-083  g-  =  42  c-c-  CO2.  The  absorption 
is  finished  in  one  minute  or  even  more  quickly ;  it  is  quite  un- 
necessary to  wait  for  it  any  longer,  as  some  have  recommended. 

In  some  cases  more  or  less  concentrated  potash  solutions 
are  employed.  Where  the  contact  between  the  gas  and  the 
absorbent  cannot  be  increased  by  shaking,  stronger  solutions 
should  be  employed.  For  Bunte's  burette,  e.g.y  the  liquor  need 
not  be  quite  so  concentrated,  but  for  the  Orsat  apparatus  it 
may  be  used  in  a  more  concentrated  state.  The  higher  its 
concentration,  the  greater  is  its  viscosity  and  its  chemical  action 
on  the  glass  of  the  vessels  employed.  Caustic  soda  has  an  even 
greater  action  on  glass,  and  is  therefore  less  recommendable  for 
the  present  purpose,  although  it  is  cheaper  than  potash.  Barium 
hydroxide  is  used  in  the  examination  of  air  by  Pettenkofer's 
method  and  its  congeners. 

Of  course  these  solutions  absorb  also  other  acid  gases, 
as  chlorine,  hydrogen  chloride,  hydrogen  sulphide,  sulphur 
dioxide,  etc. 

(b)  Absorbents  for  Heavy  Hydrocarbons. 

The  heavy  hydrocarbons  occurring  in  technical  gas-analysis 
are : — Olefins,  of  the  general  formula  C  H2n,  especially  ethylene^ 


118  TECHNICAL  GAS- ANALYSIS 

C^H^propylene,  C3H6,  and  butylene,  C4H8 ;  then  the  hydrocarbons 
of  the  series  CnH2n_2>  of  which  acetylene,  C2H2,  is  the  principal 
member  coming  into  question  ;  and  the  hydrocarbons  of  the 
benzene  series,  CwH2n_6,  of  which  benzene,  C6H6,  and  toluene, 
C7H8,  are  the  most  important.  These  hydrocarbons  are  the 
principal  illuminating  constituents  in  coal-gas,  whence  their 
estimation  in  this  gas  is  of  great  importance,  but  not  to  the 
same  extent  as  before  the  introduction  of  the  Welsbach  light. 
The  absorbents  for  them  in  gas-analysis  are  : — 

I.  Fuming  Sulphuric  Acid,  of  sp.  gr.  about  1-938,  and  con- 
taining about  20  to  25  per  cent,  "free"  SO3. — It  should  be 
borne  in  mind  that  this  reagent  must  be  kept  and  employed  at 
temperatures  above  15°,  because  below  this  some  pyrosulphuric 
acid  crystallises  out.  It  absorbs  all  the  heavy  hydrocarbons 
coming  into  question  here,  if  agitated  for  five  minutes  with  the 
gas.  Hereby  ethylene  is  converted  into  ethionic  acid,  C2H6S2O7, 
acetylene  into  acetylene-sulphuric  acid,  CgH^O^1  benzene  into 
benzene-sulphonic  acid,  C6H6SO3H. 

The  absorption  is  carried  out  in  a  simple  Hempel  gas-pipette 
(Fig.  47,  p.  82),  of  course  using  all  proper  precautions  in  filling 
it ;  in  order  to  prevent  the  attraction  of  moisture,  it  is  closed 
by  a  small  glass  rod  enlarged  at  one  end,  or  by  a  glass  cap, 
neither  of  which  parts  of  apparatus  need  be  taken  off  during 
use.  Hempel  prefers  providing  this  pipette  with  an  additional 
bulb  above  the  ordinary  one,  filled  with  bits  of  glass,  in  order 
to  enlarge  the  absorbing  surface  and  to  render  agitation 
unnecessary  (cf.  Fig.  50,  p.  85). 

After  treating  the  gases  in  the  pipette  charged  with  fuming 
sulphuric  acid,  they  must  be  freed  from  acid  vapours  by  means 
of  a  potash  pipette. 

Worstall  (/.  Amer.  Chem.  Soc.,  xxi.  p.  245)  has  observed 
that  fuming  sulphuric  acid  on  prolonged  contact  absorbs  a  little 
methane  and  ethane,  but  no  sensible  error  is  caused  by  this, 
if  the  time  of  absorption  is  not  extended  over  a  quarter  of 
an  hour. 

1  J.  Schroeder  (Ber.,  1898,  p.  2189)  states  that  fuming  sulphuric  acid 
with  acetylene  does  not  form  acetylene-sulphuric  acid  but  methionic  acid, 
CH4S2O6 ;  but  this  cannot  be  correct,  since  it  would  involve  the  formation 
of  carbon  monoxide,  which  does  not  take  place,  as  confirmed  by  Knorre  and 
Arendt  (Verh.  Geiverbfi.,  1900,  p.  166). 


ABSORBENTS  FOR  HYDROCARBONS  119 

By  this  method  only  the  total  quantity  of  heavy  hydro- 
carbons in  gases  can  be  estimated ;  methods  for  estimating 
some  of  them  separately  will  be  mentioned  in  a  subsequent 
chapter. 

2.  Bromine  Water. — This  is  a  saturated  solution  of  bromine 
in  water,  with  a  small  excess  of  bromine.  Here  also,  after 
employing  the  reagent,  the  gas  must  be  treated  with  potash 
solution,  in  order  to  remove  the  bromine  vapour.  The  reagent 
is  kept  in  a  composite  Hempel  pipette,  Fig.  52,  p.  86,  provided 
with  a  water-seal.  It  quickly  absorbs  ethylene  and  its  homo- 
logues,  transforming  them  into  bromides,  without  the  necessity 
of  agitation.  Treadwell  and  Stokes  (Ber.,  1888,  p.  3 131)  and 
Haber  and  Oechelhauser  (ibid.,  1896,  p.  2700)  have  found  the 
absorption  to  be  complete.  Acetylene  behaves  like  ethylene. 
Benzene  is  also  absorbed,  but  according  to  Winkler  (Z.  anal. 
Chem.,  1889,  p.  285)  slowly  and  incompletely.  Haber  and 
Oechelhauser  (loc.  tit.)  found  that  benzene  is  not  removed  by 
chemical  action  of  the  bromine,  but  mechanically  ;  if  benzene 
vapour  and  bromine  vapour  are  in  contact  during  two  minutes 
in  diffuse  daylight,  no  bromine  is  consumed.  Hence  ethylene 
and  benzene  cannot  be  separated  by  a  simple  treatment 
with  bromine  water ;  but  if  titrated  bromine  water  is 
employed,  the  quantity  of  ethylene  present  can  be  ascer- 
tained by  estimating  the  bromine  consumed  for  the  formation 
of  ethylene  bromide,  no  such  consumption  being  caused  by 
the  benzene.  They  first  ascertain  the  total  quantity  of  heavy 
hydrocarbons  by  means  of  fuming  sulphuric  acid,  and  treat  a 
second  sample  of  gas  with  titrated  bromine  water,  retitrating 
the  unconsumed  bromine  by  means  of  potassium  iodide  and 
sodium  thiosulphate. 

(c)  Absorbents  for  Oxygen. 

Only  a  few  of  the  numerous  reagents,  proposed  for  the 
absorptiometric  estimation  of  oxygen,  have  in  the  long  run 
proved  satisfactory. 

The  following  substances  can  be  recommended  as  thoroughly 
tested  :— 

i.  Phosphorus. — White  (yellow)  phosphorus  is  moulded  into 
thin  sticks  by  melting  it  in  a  glass  cylinder  under  warm  water 
so  as  to  form  a  layer  10  or  15  cm.  deep,  dipping  into  this  a 


120  TECHNICAL  GAS-ANALYSIS 

glass  tube  of  2  or  3  mm.  bore,  closing  this  at  the  top  with  the 
finger,  and  quickly  transferring  it  into  a  vessel  filled  with  cold 
water.  When  the  phosphorus  solidifies,  its  volume  shrinks  so 
that  the  stick  can  be  easily  pushed  out  under  water,  especially 
if  the  glass  tube  is  slightly  conical.  These  thin  sticks  are  cut 
into  smaller  sticks  under  water.  Phosphorus  moulded  in  this 
shape  can  also  be  obtained  from  the  dealers  in  chemicals. 

The  phosphorus  sticks  are  placed  in  a  suitable  vessel,  e.g.,  a 
Hempel's  tubulated  pipette,  Fig.  51,  p.  85,  where  they  are  com- 
pletely covered  with  water  and  protected  against  light.  The  water 
serves  as  a  seal ;  it  is  driven  out  by  the  gas  to  be  examined, 
which  thus  comes  into  contact  with  the  moist  phosphorus,  and 
the  absorption  of  oxygen  begins  at  once  with  formation  of 
white  clouds  of  phosphorous  acid,  which  render  the  gas  opaque 
for  some  time  without  influencing  its  volume.  If  this  process 
takes  place  in  a  dark  room,  it  produces  a  bright  light ; 
the  vanishing  of  this,  and  the  clearing  away  of  the  cloud, 
marks  the  end  of  the  process.  Generally  a  quiet  contact  of  the 
gas  with  the  phosphorus  for  two  or  at  most  three  minutes  is 
sufficient.  One  g.  phosphorus  on  being  transformed  into  phos- 
phorous acid  takes  up  0-77  g.  =  538  c.c.  oxygen  ;  hence  the  stock  of 
phosphorus  contained  in  an  absorbing-vessel  generally  lasts  for 
years  ;  but  the  water  covering  it,  which  dissolves  the  phosphorus 
and  phosphoric  acid  formed,  must  be  renewed  from  time  to 
time. 

The  following  conditions  must  be  observed  in  the  employ- 
ment of  this  reagent  : — 

(a)  Temperature. — The   absorption   should   be   carried    out 
between  15°  and  20°.     Below  15°  it  proceeds  too  slowly,  and  at 
7°  it  ceases  almost  entirely. 

(b)  Partial  Pressure  of  Oxygen. — Pure  oxygen  at  the  pressure 
of  an  atmosphere  is  not  absorbed  by  phosphorus  at  temperatures 
below  23°.     The  absorption  commences  only  when  the  gas  has 
been  reduced  by  means  of  the  air  pump  to  about  75  per  cent, 
of  the  initial  pressure ;  it  may  then  set  in  with  extreme  violence, 
or  even  explosively,  with  the  production  of  scintillations  and 
the  fusion  of  the  phosphorus.    If,  therefore,  a  gas  rich  in  oxygen, 
e.g.,  commercial  compressed  oxygen  itself,  has  to  be  examined, 
it   should   be  diluted  with   its   own   volume   of  pure  nitrogen 
(which  may  be  taken  out  of  a  phosphorus  pipette  filled  with 


ABSORBENTS  FOR  OXYGEN  121 

air)  or  pure  hydrogen.  This  should  be  done  with  all  gases 
containing  upwards  of  50  per  cent,  oxygen. 

(c)  The  Presence  of  Certain  Gases  and  Vapours  retards  or  even 
stops  in  a  hitherto  unexplained  way  the  absorption  of  oxygen 
by  phosphorus.  (Perhaps  this  phenomenon  is  analogous  to  the 
"  paralysing  "  action  of  minute  quantities  of  hydrogen  sulphide, 
carbon  disulphide,  and  some  other  substances  on  the  catalytic 
action  of  platinum  and  of  organic  ferments,  as  observed  by 
Bredigand  Miiller  von  Berneck  (Z.physzk.  Chem.,  1899,  p.  324). 
Among  the  substances  interfering  with  the  absorption  of  oxygen 
by  phosphorus  are,  according  to  Davy,  Graham,  and  Vogel, 
hydrogen  phosphide,  hydrogen  sulphide,  carbon  disulphide, 
sulphur  dioxide,  iodine,  bromine,  chlorine,  nitrogen  peroxide, 
ethylene,  acetylene,  ether,  alcohol,  petroleum,  oil  of  turpentine, 
cupione,  creosote,  benzene,  ammonia,  alcohol,  tar,  and  many 
essential  oils.  As  little  as  ^-^  vol.  PH3,  -^  vol.  C2H4,  ^fa 
vol.  oil  of  turpentine  suffice  for  producing  this  effect,  and  render 
the  application  of  phosphorus  impossible  in  such  cases.  But, 
according  to  experiments  of  Brurick,  these  disturbing  substances 
can  in  most  cases  be  removed  by  a  previous  treatment  of  the 
gas  with  fuming  sulphuric  acid,  and  after  this  the  gaseous 
mixture,  e.g.,  coal  -  gas  or  fire-damp,  may  be  treated  by 
phosphorus  for  the  absorption  of  oxygen.  This  proves  the 
incorrectness  of  some  statements  according  to  which  methane 
and  ethane  belong  to  the  class  of  substances  interfering  with  the 
absorption  of  oxygen  by  phosphorus,  since  methane  and  ethane 
are  not  removed  by  fuming  sulphuric  acid. 

This  method  renders  excellent  service  in  the  examination 
of  air,  of  chimney-gases,  of  vitriol-chamber  gases,  etc.,  and  as 
to  certainty  and  speed  of  action,  phosphorus  is  superior  to 
every  other  reagent.  Lindemann  (Z.  anal.  Chem.y  1879,  p.  158) 
has  constructed  a  special  apparatus  for  this  purpose,  which 
will  be  described  in  a  subsequent  chapter. 

(d)  The  Presence  of  Combustible  Gases. — According  to 
Baumann  (Ber.y  1883,  p.  1 146)  and  Leeds  (Chem.  News,  xlviii. 
p.  25),  carbon  monoxide  in  the  presence  of  oxygen  in  contact 
with  moist  phosphorus  is  partially  oxidised  into  carbon  dioxide. 
Remsen  and  Keiser  (Amer.  Chem.  /.,  1883,  p.  454)  contradict 
this,  but  Baumann  (Ber.,  1884,  p.  283)  maintains  his  former 
statement.  Boussingault  (Comptes  rend.y  Iviii.  p.  777)  has  shown 


122  TECHNICAL  GAS-ANALYSIS 

that  during  the  slow  combustion  of  phosphorus  in  gases 
containing  oxygen,  a  small  portion  of  combustible  gases 
present,  such  as  carbon  monoxide  or  hydrogen,  vanishes 
together  with  the  oxygen;  but  this  simultaneous  combustion 
is  comparatively  slow  and,  at  least  in  technical  gas-analysis, 
causes  no  sensible  error. 

(e)  Action  of  Light. — As  previously  mentioned,  the  absorp- 
tion vessel  filled  with  phosphorus  must  be  kept  in  the  dark. 
Otherwise  the  white  surface  of  the  phosphorus  is  covered  by 
a  thin  layer  of  red  phosphorus  which  interferes  with  the 
absorption  of  oxygen. 

A  solution  of  phosphorus  in  oil  has  been  proposed  as  a 
gas-analytical  absorbent  of  oxygen  by  Centnerszwer  (Chem. 
Zeit.)  1910,  p.  404).  It  is  prepared  by  placing  about  230  c.c. 
of  castor  oil  in  a  250  c.c.  flask,  dropping  into  the  oil  3  g.  of 
well-dried  phosphorus,  closing  the  neck  of  the  flask  with  a 
stopper,  heating  it  in  an  oil-bath  to  200°,  removing  the  flask 
from  the  bath,  and  vigorously  shaking  it  until  the  phosphorus 
is  completely  dissolved.  The  reagent  is  employed  in  a 
Hempel's  double-absorption  pipette  (Fig.  52,  p.  86),  and  the 
gas  is  allowed  to  stand  in  contact  with  it  as  long  as  a  glow 
can  be  observed.  The  results  are  correct  also  even  with  gas 
mixtures  containing  a  large  proportion  of  oxygen. 

2.  Alkaline  Solution  of  Pyrogallol. — An  aqueous  solution  of 
pyrogallol  in  contact  with  air  changes  very  slowly,  but  on  the 
addition  of  an  alkali  it  rapidly  absorbs  oxygen  and  takes  first 
a  red,  afterwards  a  deep  brown  colour.  According  to  Liebig 
(Ann.  Chem.  Pharm.,  Ixxvii.  p.  107),  I  g.  pyrogallol,  after 
addition  of  potash  solution,  absorbs  189-8  g.  oxygen  ;  according 
to  Doebereiner  (Gilb.  Ann.,  Ixxii.  p.  203 ;  Ixxiv.  p.  410),  on 
addition  of  ammonia,  266  c.c.  oxygen.  This  agrees  with 
the  results  obtained  by  Mann  in  Winkler's  laboratory, 
where  I  g.  pyrogallol,  dissolved  in  20  c.c.  potash  solution  of 
sp.  gr.  1-166,  absorbed  265-2  to  278-7,  on  the  average  268-9  c-c- 
oxygen. 

The  behaviour  of  pyrogallol  was  first  utilised  for  the 
endiometric  estimation  of  the  oxygen  in  atmospheric  air  by 
Chevreul,  in  1820,  and  was  further  investigated  by  Liebig. 
Weyl  and  Zeitler  (Ann.  Chem.  Pharm.,  ccv.  p.  255)  showed  that 
the  absorbing  action  of  pyrogallol  is  a  function  of  the  alkalinity 


ABSORBENTS  FOR  OXYGEN  123 

of  the  solution,  but  that  in  too  highly  concentrated  solutions 
of  potassium  hydrate  the  absorbing  power  is  weakened, 
probably  by  partial  decomposition  of  the  pyrogallol.  •  A  solu- 
tion of  KOH  of  sp.  gr.  1-05  was  found  suitable;  solution  of 
sp.  gr.  i -50  was  too  strong.  Winkler's  experiments  have  shown 
that  a  solution  of  caustic  potash  of  sp.  gr.  1-166,  as  employed 
for  the  absorption  of  carbon  dioxide,  is  very  suitable  indeed, 
if  50  g.  pyrogallol  are  dissolved  in  I  litre  of  it.  One  c.c.  of  this 
solution  absorbs  13  c.c.  oxygen.  This  absorption  goes  on 
more  slowly  than  that  of  carbon  dioxide,  but  it  is  usually 
complete  within  three  minutes,  if  the  gas  and  liquor  are  brought 
into  very  intimate  contact,  and  if  the  temperature  does  not  fall 
below  15°.  The  solution  is  kept  in  a  composite  gas-pipette, 
Figs.  52  and  56,  pp.  86  and  87. 

Boussingault  (Comptes  rend.,  Ivii.  p.  885)  and  Calvert  and 
Cloez  (ibid.,  pp.  870  and  875)  have  shown  that  during  the 
oxidation  of  the  alkaline  solution  of  pyrogallol  a  small  quantity 
of  carbon  monoxide  may  be  formed,  more  or  less,  depending  on 
the  energy  of  the  absorbing  process.  Pure  oxygen  yields  more 
CO  than  oxygen  diluted  with  nitrogen  or  otherwise.  The 
formation  of  CO  is  also  favoured  by  the  concentration  of  the 
absorbent.  From  100  vols.  pure  oxygen  Boussingault  obtained 
3-4,  i -02,  0-40,  0-06;  Calvert  1-99  to  4-00,  Cloez  3-50;  from 
100  vols.  oxygen  mixed  with  various  proportions  of  nitrogen, 
Boussingault  obtained  0-40,  Cloez  2-59  vols.  carbon  monoxide. 
Consequently  Boussingault  states  that,  when  employing  this 
absorbent  in  the  analysis  of  atmospheric  air,  it  may  happen 
that  the  volume  of  oxygen  is  found  o  i  or  0-2,  or  even  0-4  per 
cent,  below  the  truth.  Vivian  B.  Lewes  (/.  Soc.  Chem.  Ind., 
1891,  p.  407)  recommends  employing  the  solution  not  more  than 
four  times,  as  it  only  then  begins  to  yield  carbon  monoxide. 
He  also  recommends  keeping  it  for  twelve  hours  before  use, 
but  he  gives  no  reason  for  this.  Contrary  to  all  these  state- 
ments, Poleck  (Z.  anal.  Chem.,  1869,  p.  451),  when  specially 
examining  this  source  of  error  in  researches  on  the  composition 
of  air,  could  not  find  even  traces  of  carbon  monoxide  formed  by 
the  employment  of  pyrogallol,  and  he  therefore  recommends  it 
as  perfectly  reliable  in  the  case  of  moderate  percentages  of 
oxygen.  The  same  observation  is  made  in  technical  gas- 
analysis  ;  at  all  events  the  amount  of  CO  evolved  is  too  small 


124  TECHNICAL  GAS-ANALYSIS 

to   sensibly  influence   the   determinations   of  oxygen   by  this 
method,  except  in  the  analysis  of  "pure"  oxygen. 

The  alkaline  solution  of  pyrogallol  of  course  equally  absorbs 
carbon  dioxide,  and  this  gas  must  therefore  be  previously 
removed  before  commencing  the  absorption  of  oxygen. 

3.  Copper  (A  m moniacal  Cuprous  Oxide}. — Those  metals  which 
form  soluble  ammonia  compounds,  like  copper,  zinc,  and  cadmium 
in  contact  with  ammonia  and  oxygen,  are  transformed  into  the 
respective  compounds  with  absorption  of  oxygen.  Lassaigne 
and  later  on  Hempel  (Gasanal.  Methoden,  1900,  p.  142) 
have  applied  this  behaviour  for  the  estimation  of  oxygen. 
Copper  is  preferred  to  the  other  metals,  because  it  dissolves 
without  the  evolution  of  hydrogen,  and  because  it  can  be 
employed  in  the  shape  of  thin  wire  gauze  offering  a  large  absorb- 
ing surface.  A  tubulated  gas-pipette  (Fig.  51,  p.  85)  is  charged 
with  small  coils  of  such  wire  gauze  and  with  a  mixture  of  equal 
volumes  of  a  saturated  solution  of  commercial  ammonium 
carbonate  and  of  liquor  arnmoniae,  of  sp.  gr.  0-96.  If  a  gas 
containing  oxygen  is  introduced  into  such  a  pipette,  the  oxygen 
is  absorbed  without  any  agitation  in  less  than  five  minutes. 
Probably  at  first  a  compound  of  ammonia  with  cuprous  oxide  is 
formed,  which  absorbs  a  further  quantity  of  oxygen  and  thus 
yields  a  compound  of  ammonia  with  cupric  oxide,  which,  in 
contact  with  the  copper  present  in  excess,  is  retransformed  into 
the  cuprous  compound.  This  would  mean  that  I  g.  copper  can 
absorb  177  c.c.  of  oxygen. 

The  application  of  this  absorbent  has  the  advantage  that 
copper  moistened  with  liquor  ammonias  absorbs  oxygen  much 
more  quickly  than  the  alkaline  solution  of  pyrogallol,  and  more 
conveniently,  as  there  is  no  necessity  for  agitation.  Its 
efficiency  is  nearly  equal  to  that  of  phosphorus,  and  its 
advantage  over  the  latter  is  that  it  is  absolutely  harmless  and 
that  it  acts  down  to  a  temperature  of  —  7°.  But  its  use  is 
restricted  by  the  fact  that  it  absorbs  equally  well  carbon 
monoxide,  which  is  present  in  many  cases  where  the  oxygen 
has  to  be  determined.  It  absorbs  also  ethylene  and  acetylene, 
the  latter  with  formation  of  red  explosive  copper  acetylide. 
Before  employing  it,  any  carbon  dioxide  present  must  of  course 
be  removed. 

Red-hot  copper  is  used  for  the  absorption  of  oxygen  in  the 


ABSORBENTS  FOR  OXYGEN  125 

"  Copper  Eudiometer"  of  Kreusler  (  Wiedemanrfs  Ann.  N.F.,  vi. 
p.  537  ;  Hempel's  GasanaL  Methoden,  4th  ed,  p.  309). 

4.  Sodium   Hydrosulphite  (Franzen,  Ber.,   1906,  p.  2069).  — 
This  compound  acts  according  to  the  following  equation  :  — 


=   NaHSO4  +  NaHSO3. 

Its  absorbing  value  is  very  great  ;  I  g.  of  it  absorbs  about 
128  c.c.  oxygen.  It  is  used  in  weakly  alkaline  solution  in 
Hempel's  absorbing  pipettes,  for  which  purpose  Frenzel 
recommends  a  solution,  prepared  by  mixing  a  solution  of 
50  g.  commercial  sodium  hydrosulphite  (cost  price  2s.  6d. 
per  kilogramme)  in  250  c.c.  water  with  40  c.c.  of  a  solution 
of  500  g.  caustic  soda  in  700  c.c.  water.  For  use  in  a  Bunte 
burette  a  less  concentrated  solution  is  employed,  consisting 
of  10  g.  sodium  hydrosulphite  in  50  c.c.  water,  mixed  with 
50  c.c.  of  a  10  per  cent,  caustic  soda  solution. 

The  advantage  of  this  reagent  over  phosphorus  is  that 
the  substances  which  prevent  the  oxidation  of  phosphorus  are 
without  influence  on  the  hydrosulphite.  Its  advantages  over 
the  alkaline  solution  of  pyrogallol  are  the  cleaner  work,  the 
greater  cheapness,  and  the  higher  degree  of  action.  It  is  also 
independent  of  the  temperature,  and  it  absorbs  no  carbon 
monoxide  (cf.  No.  3). 

5.  Chromium    Protochloride   is   recommended    by   von    der 
Pfordten    (Annalen,   ccxxviii.    p.     112)    as    an    absorbent    for 
oxygen  which  does  not  act  on  hydrogen  sulphide  and  carbon 
dioxide.     It  is  prepared  by  heating   chromic   acid  with  con- 
centrated    hydrochloric    acid     to    green    chromium    chloride, 
which  is  then  reduced  to  protochloride  by  reducing  with  zinc 
and  hydrochloric  acid,  filtered  and  run  into  a  saturated  solution 
of  sodium  acetate  ;  red  chromium  acetate  is  precipitated  which 
is  separated  by  filtration,  washed  and  decomposed  by  hydro- 
chloric acid,  air  being  excluded. 

6.  Alkaline  Solution  of  Ferrous   Tartrate,  proposed  by  De 
Koninck  (Z.  angew.  Chem.,  1890,  p.  727),  is  less  efficient  than 
the  other  agents  described  here. 

The  absorbents  employed  for  estimating  oxygen  in  the 
form  of  ozone  will  be  described  later  on  when  specially  treating 
of  that  substance. 


126  TECHNICAL  GAS-ANALYSIS 

(d)  Absorbents  for  Carbon  Monoxide. 

The  general  absorbent  for  carbon  monoxide  is  a  solution 
of  cuprous  chloride,  CuCl,  which  combines  with  it  to  form 
carbonyl-cuprous-chloride.  According  to  Manchot  and  Friend 
(Annalen,  1908,  ccclix.  p.  100),  the  process  is  : 

CuCl  +  CO  +  2H2O  ^  CuCl,  2H20,  CO. 

Hence  there  is  an  equilibrium  between  the  two  sides  of  the 
equation,  and  the  absorption  of  carbon  monoxide  by  a  hydro- 
chloric acid  solution  of  cuprous  chloride,  for  which  the  above- 
given  equation  is  valid,  can  never  be  complete.  On  the 
contrary,  a  long-used  absorbing  solution,  which  contains  much 
of  the  copper-carbonyl-chloride,  may  yield  up  carbon  monoxide 
by  dissociation  to  gaseous  mixtures  containing  but  little  carbon 
monoxide.  For  this  reason  it  is  generally  preferred  to  employ 
the  ammoniacal  solution  of  cuprous  chloride,  with  which  the 
absorption  of  carbon  monoxide  is  practically  quantitative,  as  the 
easily  dissociating  cuprous-chloride-carbon-monoxide  is  continu- 
ously removed  by  a  secondary  reaction,  by  which  ammonium 
carbonate  and  chloride  and  metallic  copper  are  formed. 

2(CuCl,CO)  +  4NH3  +  2H20   =   Cu2  +  CO  .  O  .  NH4  +  2NH4C1. 

CO  .  O  .  NH4 

The  free  copper  protects  the  solution  against  oxidation  and 
reduces  any  cupric  chloride  formed  to  cuprous  chloride. 

Pfeiffer  (Lunge  and  Berl,  Chem.  techn.  Unt.  Methoden,  6th  ed., 
1911,  iii.  p.  239)  prepares  an  acid  solution  by  pouring  250  c.c. 
concentrated  hydrochloric  acid  over  35  g.  commercial  cuprous 
chloride,  placing  some  copper-wire  net  in  the  solution  and 
keeping  it  protected  from  air  until  it  has  turned  colourless. 
This  solution  is  then  poured  into  about  1-5  litre  water,  whereby 
white  cuprous  chloride  is  precipitated.  After  twenty-four  hours 
the  clear  liquor  above  this  is  poured  off  and  the  cuprous  chloride 
is  dissolved  in  250  c.c.  liquor  ammoniae  of  sp.  gr.  0-91. 

Sandmeyer  (Berl.  Ber.^  1884,  p.  1633)  describes  another  way 
of  preparing  this  solution.  A  very  suitable  solution  of 
cuprous  chloride,  sufficiently  ammoniacal,  but  with  slight 
vapour  tension,  is  prepared  as  follows : — 250  g.  of  ammonium 
chloride  is  dissolved  in  750  c.c.  of  water  in  a  bottle  provided 


ABSORBENTS  FOR  CARBON  MONOXIDE  127 

with  a  good  india-rubber  cork,  and  to  this  is  added  200  g. 
cuprous  chloride ;  a  metallic  copper  spiral,  reaching  from  top 
to  bottom,  is  inserted.  The  cuprous  chloride  dissolves  on 
frequent  agitation,  leaving  behind  a  little  cupric  oxychloride, 
and  forming  a  brown  liquid  which  keeps  an  indefinite  time, 
if  air  is  excluded.  In  contact  with  air  a  precipitate  of  green 
cupric  oxychloride  is  formed.  Before  use,  this  solution  is 
mixed  with  one-third  its  volume  of  liquor  ammoniae,  sp.  gr.  0-910. 
It  is  usually  kept  in  Hempel  pipettes  with  a  water  seal, 
provided  at  the  lowest  point  of  the  connecting  tube  with 
a  branch  tube,  fitted  with  a  pinchcock,  to  facilitate  the  charging 
(Fig.  53,  p.  87).  The  pipette  is  charged  by  connecting  the 
open  end  of  the  pinchcock  tube  with  a  rubber  tube  reaching 
above  the  top  of  the  pipette,  putting  a  funnel  into  the  tap, 
and  pouring  in  at  first  50  c.c.  liquor  ammoniae  and  then  150  c.c. 
of  the  stock  solution  of  cuprous  chloride,  whereupon  the 
charging  tube  is  taken  off  and  the  outer  end  of  the  pinchcock 
tube  closed  by  a  bit  of  glass  rod. 

One  c.c.  of  this  solution  absorbs  16  c.c.  carbon  monoxide. 
But  since  this  gas  is  held  so  loosely  that  the  combination  is 
destroyed  to  a  slight  extent  even  by  a  decrease  of  pressure, 
as  found  by  Tamm  {Jernkontorets  Annaler,  vol.  xxxv.)  and 
Drehschmidt  (Ber.,  1887,  p.  2752)  the  latter  (Ber.  1888, 
p.  2158)  recommends  using  two  pipettes  in  series,  the  first 
of  which  is  charged  with  a  several  times  used  solution  of 
ammoniacal  cuprous  chloride,  which  absorbs  the  principal 
portion  of  the  carbon  monoxide  present,  whilst  the  second 
pipette  contains  a  fresh  and  consequently  very  active  solution 
of  the  same  reagent  which  takes  up  the  last  traces  of  carbon 
monoxide.  These  two  pipettes  should  be  provided  with  labels 
of  different  colour,  to  prevent  mistakes. 

According  to  Gautier  and  Clausmann  (Comptes.  rend.,  cxlii. 
p.  485  of  1906)  the  last  traces  of  carbon  monoxide  cannot  be 
removed  in  this  way.  They,  as  well  as  Nowicki  (ibid.^  p.  1186), 
recommend  removing  this  small  remainder  of  carbon  monoxide 
by  passing  the  gas  over  anhydrous  iodic  acid  at  70°,  and  either 
estimating  the  CO2  formed  by  passing  the  gas  into  baryta  water, 
or  estimating  the  iodine  liberated  by  the  reaction  by  titration 
with  arsenious  acid,  or  colorimetrically  with  potassium-iodide- 
starch  solution  in  a  solution  in  benzene  or  chloroform.  This 


128  TECHNICAL  GAS-ANALYSIS 

method  is  especially  intended  for  proving  the  presence  of  traces 
of  CO  in  atmospheric  air. 

The  ammoniacal  cuprous  chloride  solution  absorbs  also 
carbon  dioxide,  heavy  hydrocarbons  (especially  acetylene  and 
ethylene),  and  oxygen,  all  of  which  must  therefore  be  removed 
before  estimating  the  carbon  monoxide. 

The  prescription  for  employing  the  ammoniacal  cuprous 
chloride  solution  in  the  Bunte  burette  is:  agitating  the  gas 
with  it  for  one  minute,  drawing  off  the  solution,  replacing  it  by 
fresh  solution,  agitating  again,  and  repeating  this  at  least  twice. 
After  the  last  drawing  off,  run  3  to  4  c.c.  concentrated  hydro- 
chloric acid  from  the  funnel  into  the  burette,  then  water  which 
forms  a  layer  on  the  acid,  draw  off  the  liquid,  wash  with  water, 
draw  in  I  to  2  c.c.  caustic  potash  solution,  agitate,  allow  water 
to  enter,  place  the  liquids  on  a  level,  and  read  off. 

Czako  (/".  Gasbeleucht.)  1914,  p.  169)  points  out  that  the 
cuprous  chloride  solution  should  be  colourless.  No  more  than 
5  c.c.  of  it  should  be  put  into  the  burette,  without  any  violent 
shaking,  and  this  must  be  twice  repeated. 

The  application  of  this  reagent  to  a  qualitative  and  an 
approximate  colorimetrical  estimation  of  carbon  monoxide  will 
be  mentioned  later  on. 

(e)  Absorbents  for  Nitrogen. 

Such  an  absorbent  is  used  for  the  isolation  of  argon  and  its 
congeners.  Hempel  (Z.  anorg.  Chem.,  1899,  xxi.  p.  19)  has 
shown  that  nitrogen  is  absorbed  at  a  red  heat  by  a  mixture  of 
I  part  magnesium  powder  with  5  parts  freshly  ignited  calcium 
oxide  and  0-25  parts  sodium.  I  g.  of  this  mixture  absorbed  by 
an  hour's  contact  52  c.c.  of  nitrogen. 

Franz  Fischer  (Berl.  Ber.,  1908,  p.  2017)  showed  that  calcium 
carbide  may  be  employed  for  the  absorption  of  nitrogen, 
together  with  oxygen,  leaving  behind  the  gases  of  the  argon 
group.  An  apparatus  for  this  purpose,  founded  upon  an  auto- 
matic device  of  Collie  (/.  Chem.  Soc.,  1889,  p.  no),  has  been 
constructed  by  Travers  (Dennis,  Gas  Analysis,  pp.  209  et  seq.\ 

(f)  A  bsorbents  for  Nitric  Oxide. 

Nitric  oxide,  NO,  is  soluble  in  sulphuric  acid  of  various 
concentrations.  According  to  Lubarsch  (as  quoted  by  Hempel, 


ABSORPTION  OF  HYDROGEN 


129 


Gasanal.  Methoden,  4th  ed,  p.   181),  100  vols.  of  sulphuric  acid 
absorb : — 


Per  cent.  H2SO4. 

Vols.  NO. 

Monohydrate,  H2SO4 

100-0 

3-5 

H2SO4  +  2-5H2O 

68-5 

H 

H2S04  +  9H20. 
H2SO4+I7H2O 

45-5 
377 
24-3 

2.0 
2-7 

4-5 

Pure  water        . 

o-o 

7-2 

The  ordinary  absorbent  for  nitric  oxide  is  a  solution  of 
i  part  crystallised  ferrous  sulphate  in  2  parts  water,  which 
absorbs  3  vols.  NO.  A  saturated  solution  of  ferrous  chloride 
(which  must  be  slightly  acidified,  to  prevent  frothing)  absorbs 
twenty-two  times  its  volume  of  NO  ;  carbon  dioxide  is  equally 
soluble  therein,  and  must  therefore  be  previously  removed  by 
caustic  alkali.  In  these  solutions  the  NO  is  very  loosely  bound 
and  partially  removed  by  shaking. 

Knorre  (Chem.  Ind.y  p.  534)  absorbs  NO  by  a  saturated 
solution  of  potassium  bichromate,  to  which  one-fifth  of  its 
volume  of  concentrated  sulphuric  acid  has  been  added. 

This  is  preferable  to  potassium  permanganate,  which  has 
been  used  for  the  same  purpose. 


(g)  Hydrogen 

can  be  absorbed  by  finely  divided  palladium,  according  to 
Graham  (Chem.  Centr.,  1869,  p.  719)  and  Hempel  (Ber.,  1879, 
pp.  636  and  1006).  Generally  hydrogen  is  estimated  by  com- 
bustion with  oxygen  (or  air),  as  we  shall  see  below;  but 
Hempel  employs  Graham's  reaction  for  analysing  mixtures  of 
hydrogen  and  methane,  by  first  absorbing  the  hydrogen  by 
palladium  sponge,  and  then  burning  the  methane  by  explosion ; 
and  he  has  worked  out  the  conditions  for  performing  these 
operations  quantitatively. 

Pure  palladium  is  indifferent  towards  a  mixture  of  hydrogen, 
methane,  and  nitrogen,  but  if  it  contains  a  small  proportion  of 
palladious  oxide,  a  partial  combustion  of  hydrogen  takes  place, 
and  the  heat  thus  generated  is  sufficient  to  ensure  the  absorption 

I 


130 


TECHNICAL  GAS-ANALYSIS 


of  the  rest  of  the  hydrogen  present ;  the  process  is  accordingly 
partly  a  combustion  and  partly  an  occlusion  of  hydrogen. 

The  palladium  is  prepared  by  heating  4  or  5  g.  palladium 
sponge,  in  portions  of  I  g.  at  a  time,  on  the  lid  of  a  platinum 
crucible,  until  it  nearly  glows,  and  then  allowing  it  to  cool 
slowly,  whereby  a  thin  film  of  oxide  is  formed  upon  the  surface 
of  the  metal.  For  use,  4  g.  of  this  oxidised  sponge  is  placed  in 
a  U-tube  of  4  mm.  internal  diameter  and  20  cm.  long;  the 
tube  is  placed  in  a  beaker,  as  shown  in  Fig.  66,  and  kept  at  a 
temperature  of  90°  to  100°  by  hot  water.  To  carry  out  a 


FIG.  66. 

determination,  the  |J'tuDe  'ls  attached  on  one  side  to  the 
burette,  and  on  the  other  to  a  pipette  charged  with  water,  and 
the  gas  syphoned  backwards  and  forwards  three  times  ;  the 
beaker  H  is  then  replaced  by  a  beaker  containing  cold  water, 
and  the  gas  again  passed  twice  through  the  tube,  so  as  to  cool 
it  to  the  original  temperature.  The  volume  is  finally  adjusted 
by  syphoning  the  liquid  in  the  pipette  up  to  z,  and  the  reading 
is  taken ;  the  decrease  in  volume  represents  the  absorbed 
hydrogen  and  the  volume  of  oxygen  originally  contained 
in  the  LJ-tube.  The  latter  is  determined,  once  for  all,  by  closing 


ABSORPTION  OF  HYDROGEN  131 

one  end  of  the  |J-tube  with  a  glass  stopper  attached  by  a  piece  of 
rubber  tubing,  and  then  placing  it  in  a  beaker  of  water  at  9° ; 
the  open  end  of  the  tube  is  then  connected  with  the  burette, 
previously  filled  with  water,  and  the  tube  heated  in  the  beaker 
to  100°.  The  increase  of  volume,  as  measured  in  the  burette, 
is  that  due  to  an  increase  of  91°  in  temperature,  and  therefore 
equal  to  one-third  of  the  volume  of  gas  ;  from  this  value  the 
volume  of  oxygen  in  the  (J-tube  is  obtained.  The  palladium  is 
regenerated  after  use  by  first  passing  air  over  it,  when  it  gets 
quite  hot ;  any  drops  of  water  that  may  collect  are  removed,  the 
palladium  is  then  shaken  out  of  the  tube  and  superficially 
oxidised  as  before  by  heating  on  the  lid  of  a  platinum  crucible. 

Carbon  dioxide  and  monoxide,  oxygen,  heavy  hydrocarbons, 
and  vapours  of  hydrochloric  acid  and  of  ammonia,  prevent  the 
determination  of  hydrogen  by  this  method,  and  it  is  but  rarely 
used  in  technical  gas-analysis.  It  has,  however,  the  advantage 
that  since  no  air  is  added,  there  is  no  restriction  as  to  the 
volume  of  gas  to  be  used  for  the  analysis. 

Palladium  hydrosol  (sold  in  a  solution  of  61  to  63  per  cent, 
by  Kalle  &  Co.,  Biebrich  on  Rhine,  by  the  name  of  Palladiumsol\ 
according  to  Paal  and  Gerun  (Ber.,  1908,  p.  808),  absorbs  up 
to  3000  times  its  volume  of  hydrogen.  Paal  and  Hartmann 
(Ber.,  1910,  p.  243)  employ  a  solution  of  2-44  g.  palladiumsol 
with  2-74  g.  sodium  picrate  (which  acts  as  an  oxidiser)  in 
130  c.c.  water.  The  liquid  is  kept  in  one  of  the  Hempel 
pipettes,  and  if  not  in  use  must  be  protected  against  light  and 
air.  The  absorption  of  the  hydrogen  takes  place  within  ten 
minutes  without  requiring  any  shaking,  but  previously  all  other 
absorbable  gases,  also  carbon  monoxide,  should  be  removed. 

Brunck  (Chem.  Zeit.^  1910,  pp.  1313  and  1331)  employs  for 
absorbing  hydrogen  a  solution  of  2  g.  colloidal  platinum 
+  5  g.  picric  acid,  neutralised  by  22  c.c.  normal  caustic  soda 
solution,  diluted  with  water  to  100  to  no  c.c.  The  firm  of 
Kalle  &  Co.,  at  Biebrich,  supply  the  mixture  in  such  a  shape 
that  it  needs  only  to  be  dissolved  in  100  c.c.  of  water,  at  the 
price  of  los.  per  gramme.  This  solution  absorbs  theoretically 
4369  c.c.  hydrogen  of  o°  and  760  mm.  pressure.  The  absorption, 
if  promoted  by  frequent  shaking,  takes  ten  to  thirty  minutes. 
By  this  method  it  is  possible  to  estimate  hydrogen  in  the 
presence  of  saturated  hydrocarbons. 


132  TECHNICAL  GAS-ANALYSIS 


(h)  Absorbents  for  Unsaturated  Hydrocarbons. 

Lebeau  and  Damiens  (Comptes  rend.,  1913,  clvi.  pp.  557 
et  seq.}  use  as  absorbing  agent  for  acetylene  and  its  homologue 
a  solution  containing  25  g.  of  mercuric  iodide  and  30  g.  of 
potassium  iodide  in  100  c.c.  of  water,  with  addition  of  a  fragment 
of  caustic  potash.  This  reagent  absorbs  20  times  its  volume 
of  acetylene,  forming  a  white  precipitate.  Olefines  are  only 
dissolved  by  this  reagent  to  the  same  extent  as  by  pure  water. 
For  the  absorption  of  olefines,  sulphuric  acid  is  used,  the 
absorption  being  made  much  more  rapid  by  dissolving  i  g.  of 
vanadic  anhydride,  or  6  g.  of  uranyl  sulphate,  in  100  g.  sulphuric 
acid  sp.  gr.  1-84. 

Acetylene  is  also  absorbed  by  an  ammoniacal  solution  of 
cuprous  chloride,  by  which  a  reddish  brown  precipitate  of 
Cu2C2  is  formed,  which  is  filtered  off,  washed  with  dilute 
ammonia  till  this  runs  off  colourless,  collected  in  a  Gooch 
crucible,  and  dried  over  calcium  chloride  at  100°  in  a  current 
of  carbon  dioxide.  Dry  copper  acetylide  may  explode  already 
at  60°.  This  risk  is  avoided  by  not  drying  the  moist  Cu2C2, 
but  determining  the  copper  contained  in  it  (Scheiber,  BerL  Ber.y 
1908,  p.  3816). 

Acetylene  can  be  also  determined  by  absorbing  it  m  fuming 
sulphuric  acid  by  means  of  a  Hempel  pipette. 


^.—ESTIMATION  OF  GASES  BY  TITRATION. 
General  Remarks. 

Sometimes  one  (or  several)  of  the  constituents  of  a  gaseous 
mixture  is  estimated  not  as  described  in  the  last  chapter,  by 
the  contraction  of  volume  of  the  gas  ensuing  on  the  removal 
of  that  constituent  by  an  absorbent,  but  by  chemical  examina- 
tion of  the  latter.  This  may  be  done  in  various  ways ;  in  this 
section  we  treat  of  the  estimation  by  titration,  which  in  the 
nature  of  things  can  take  place  only  in  the  case  of  constituents 
endowed  with  sufficiently  great  chemical  affinities,  and  is  then 
carried  out  wherever  possible,  especially  for  technical  purposes. 

For  this  purpose  the  ordinary  standard  solutions,  as  generally 
used  in  volumetric  analysis,  may  be  employed.  In  many  cases, 


TITRATION  OF  GASES  133 

however,  it  is  preferable  to  prepare  special  standard  solutions, 
not  indicating  the  weight  but  the  volume  of  the  gas  in  question. 
A  "normal  solution"  is  then  that  of  which  I  c.c.  corresponds 
to  exactly  i  c.c.  of  the  gas  to  be  absorbed,  assumed  to  be  in 
the  normal  state,  i.e.,  at  a  pressure  of  760  mm.  of  mercury,  at 
a  temperature  of  o°,  and  absolutely  dry.  A  decinormal  solution 
is  one  of  which  I  c.c.  corresponds  to  o- 1  c.c.  of  the  gas.  Some- 
times, as  in  ordinary  volumetric  analysis,  viz.,  where  a  gas  is 
not  estimated  directly,  but  by  retitration,  two  standard  liquids 
are  required.  The  relation  between  these  must  be  exactly 
known ;  and  in  some  cases  it  is  not  possible  to  employ 
"normal"  solutions,  but  solutions  of  which  the  chemical  effect 
of  which  is  empirically  determined. 

The  titration  of  the  constituents  sought  for  may  either  take 
place  while  measuring  the  total  volume  of  the  gaseous  mixture, 
or  the  non-absorbable  residue  of  gas  may  be  measured,  which 
remains  after  passing  the  gas  through  an  apparatus  containing 
a  known  volume  of  titrated  absorbing  liquid,  in  which  case  the 
sum  of  the  amount  calculated  from  the  titration  and  that 
measured  directly  corresponds  to  the  total  volume  of  gas 
employed. 

In  the  first  case,  that  where  the  total  volume  of  the  gas  is 
directly  measured,  we  must  distinguish  between  such  estimations 
for  which  only  a  comparatively  small  quantity  of  gas  is 
employed,  and  such  where  a  large  quantity  of  gas  has  to 
be  continually  examined.  In  the  latter  case,  the  gas  to  be 
tested  is  passed  through  a  gas-meter  in  which  the  quantity 
passing  through  is  recorded  ;  on  going  out  of  the  meter  the 
gas  is  made  to  traverse  a  vessel  charged  with  a  measured 
quantity  of  absorbing  liquid,  which  after  certain  intervals,  when 
a  sufficient  quantity  of  gas  has  passed  through,  is  retitrated. 

Where  only  a  limited  quantity  of  gas  is  at  disposal,  it  is 
measured  in  a  flask  of  known  capacity  up  to  a  mark  in  its  neck, 
to  which  the  rubber  cork  closing  the  neck  is  pressed  down. 
This  cork  has  two  perforations,  one  for  the  tube  for  passing  the 
gas  into  the  flask,  the  other  for  the  delivery  tube  of  the  pipette 
or  burette  used  in  titration,  as  shown  in  Fig.  67,  p.  134.  After 
filling  the  flask  with  the  gas,  the  tube  through  which  this  has 
been  effected  is  closed  with  a  glass  rod,  which  is  taken  out  for  a 
moment  in  order  to  remove  the  excess  pressure  after  running 


134 


TECHNICAL  GAS-ANALYSIS 


a  liquid  into  the  flask.  In  order  to  estimate  the  constituent  in 
question,  a  certain  volume  of  a  titrated  liquid  is  run  by  means 
of  a  pipette  or  burette  into  the  flask,  which  of  course  causes  the 
same  volume  of  gas  to  escape  on  opening  the  other  tube  for  a 
moment,  this  volume  being  deducted  on  calculation  of  the  result 
from  the  total  contents  of  the  flask.  After  agitating  the  flask, 
the  excess  of  the  absorbent  is  estimated  by  retitration. 

In  the  second  class  of  titration  methods,  either  a  measured 

excess  of  absorbent  is  employed, 
which  is  afterwards  retitrated,  or 
else  the  gas  is  passed  through  a 
limited  quantity  of  the  absorbent 
until  a  visible  reaction,  e.g.,  a 
change  of  colour,  proves  that  the 
active  constituent  of  the  absorbing 
liquid  has  been  just  saturated.  The 
volume  of  the  unabsorbed  part  of 
the  gas  is  found  by  a  measuring 
apparatus  attached  to  the  absorb- 
ing vessel,  which  is  either  con- 
nected with  an  aspirating  arrange- 
ment, or  acts  itself  as  such.  Such 
measuring  apparatus,  according  to 
the  quantity  of  gas  and  to  the 
desired  degree  of  accuracy,  may 
be  either  an  ordinary  gas-meter, 
or  a  water  aspirator,  or  an  india- 
rubber  pump  which  at  each  stroke 
aspirates  approximately  equal  vol- 
umes of  gas.  If  the  estimation  of 
the  constituent  to  be  determined  is  effected  by  employ- 
ing an  excess  of  the  absorbing  liquid  and  retitration  the 
experiment  may  be  continued  until  the  unabsorbable  portion 
of  the  gas  has  reached  a  certain  volume,  to  be  measured  either 
by  an  automatically  shutting-off  gas-meter,  or  by  an  aspirator 
from  which  a  definite  quantity  of  water  is  run  off.  In  that  case 
the  non-absorbable  portion  of  the  gas  is  a  constant,  the 
absorbable  portion  a  variable  magnitude. 

It  must  be  borne  in  mind  that  the  total  volume  of  gas,  or 
that   which  remains   after  absorption,  is  measured    under   the 


FIG.  67. 


APPARATUS  OF  HESSE 


135 


varying  conditions  of  atmospheric  pressure  and  temperature, 
whilst  the  titration  of  the  absorbed  gas  indicates  this  in  the 
" normal"  state  (760  mm.  and  o°C).  Of  course  for  somewhat 
exact  analysis  both  volumes  must  be  reduced  to  the  same 
conditions. 

We  now  enumerate  some  apparatus  constructed  for  carrying 
out  the  estimation  of  gases  by  titration. 

i.  Apparatus  of  Hesse. — This  is  represented  by  the  cut, 
Fig-  67,  P-  J34-  I*  shows  a  conical  bottle  of  strong  white  glass, 


FIG.  68. 

holding  about  500  or  600  c.c.,  with  a  mark  in  the  neck  (the  contents 
up  to  which  point  are  etched  on  the  glass)  with  a  rubber  cork, 
through  the  perforations  of  which  an  inlet-pipe  and  a  pipette  or 
burette  can  be  introduced  ;  otherwise  they  are  closed  by  glass 
rods.  In  order  to  take  the  sample,  the  bottle  is  filled  with 
water,  a  portion  of  which  is  then  displaced  by  the  gas  to  be 
examined,  whereupon  the  cork  with  its  glass  stoppers  is  put  in 
and  pressed  down  to  the  mark.  If  the  employment  of  water 
must  be  avoided,  for  instance  when  taking  a  sample  of  air 
contained  in  the  soil,  as  shown  in  Fig.  68,  the  rubber  stoppers 


136  TECHNICAL  GAS-ANALYSIS 

provided  with  an  inlet-  and  outlet-tube  is  put  in  the  dry  bottle, 
and  the  gas  is  drawn  into  it  by  means  of  a  rubber  pump. 
When  this  has  been  done,  the  end  of  the  inlet-pipe  is  drawn 
out  of  the  stopper,  and  both  openings  of  this  are  quickly  closed 
by  their  glass  rods.  An  excess  of  a  standard  solution  is  now 
run  in,  and  the  volume  of  gas  corresponding  to  this  is  deducted 
from  the  total.  When  the  action  of  the  absorbent  on  the  gas 
has  been  completed  by  gentle  shaking,  the  cork  is  taken  out 
and  the  excess  of  absorbent  is  found  by  retitration. 

The  following  are  some  of  the  applications  of  this  appar- 
atus : — 

(a)  Estimation  of  carbon  dioxide  in  atmospheric  air,  from 
rooms,  pits,  caves,  subsoil,  in  coal-gas,  etc.  Titrated  baryta 
water  is  employed  as  absorbent,  normal  (or  decinormal)  oxalic 
acid  for  retitration,  and  phenolphthalein  as  indicator.  The 
baryta  water,  which  is  too  changeable  for  being  made 
permanently  normal,  is  employed  of  an  approximately  normal 
strength,  and  checked  from  time  to  time  by  the  normal  oxalic 
acid,  which  in  this  case  should  not  be  replaced  by  mineral 
acids,  as  it  has  over  them  the  advantage  of  not,  or  but  very 
slowly,  acting  on  the  barium  carbonate  formed. 

(ft)  Estimation  of  hydrogen  chloride  in  the  gases  from  salt- 
cake  furnaces,  hydrochloric-acid  condensers,  calcining  furnaces 
for  copper  extraction  by  the  wet  process,  etc.  Here  a  normal 
silver  nitrate  solution  is  employed  for  absorption,  a  normal 
solution  of  ammonium  sulphocyanide  for  retitrating  and  a 
solution  of  iron-alum  as  indicator.  Or  else  the  HC1  is  absorbed 
by  a  solution  of  potassium  hydrate,  which  is  afterwards 
acidulated  with  nitric  acid  and  titrated  by  Volhard's  process. 
Or  else  a  solution  of  sodium  carbonate  is  employed  for 
absorbing  the  HC1,  retitrating  the  excess  by  normal  silver 
nitrate  solution,  with  potassium  chromate  as  indicator. 

(c)  Estimation  of  chlorine  in  the  gases  from  chlorine  stills, 
from   the   Deacon   process,   in    the    air    of   bleaching-powder 
chambers,    etc.       The    absorbent    is    a    normal     solution     of 
arsenious    acid    in    sodium     bicarbonate,    the     excess    being 
retitrated  by  normal  iodine  solution,  with   starch   solution   as 
indicator. 

(d)  For  estimating  both   chlorine  and  hydrogen  chloride  a 
second    volume   of  gas    is   employed,  the   absorbent   for   this 


APPARATUS  OF  REICH-LUNGE  137 

being  a  solution  of  arsenious  acid  in  sodium  carbonate ;  this  is 
afterwards  acidulated  with  nitric  acid,  and  the  total  HC1,  viz., 
that  originally  present  plus  that  formed  from  the  chlorine,  is 
titrated  as  above-mentioned  with  silver  solution  and  ammonium 
sulphocyanide.  Since  each  volume  of  chlorine  produces  two 
volumes  of  HC1,  twice  the  volume  of  the  free  chlorine  must  be 
deducted  from  the  total  volume  of  HC1. 

Both  in  this  case  and  the  last,  it  is  more  important  to 
ascertain  the  weight  of  HC1  and  Cl  than  the  volume.  It  is 
therefore  preferable  here  not  to  make  the  calculations  by 
volume,  but  to  employ,  in  lieu  of  the  "normal"  solutions 
otherwise  used  in  gas-analysis,  i.e.,  such  as  indicate  I  c.c.  of 
gas  per  i  c.c.  of  the  reagent,  the  "decinormal"  solutions  of 
ordinary  volumetric  analysis,  or  else  solutions  indicating 
o-ooi  grain  per  cubic  centimetre,  or  parts  of  a  grain  as  the 
case  may  be. 

(e)  Estimation  of  sulphur  dioxide  in  the  gases  of  pyrites- 
kilns,  chimneys,  glass-houses,  etc.  The  absorption  is  performed 
by  a  solution  of  sodium  carbonate  of  arbitrary,  but  not  too 
high  strength ;  a  little  starch  solution  is  added  and  the  re- 
titration  made  by  iodine  solution. 

2.  Apparatus  of  Reich  (as  modified  by  Lunge),  Fig.  69. 
This  belongs  to  that  class  of  apparatus  where  the  non-absorbed 
gaseous  remainder  is  measured.  The  bottle  A,  holding  about 
a  litre,  is  about  half  filled  with  the  absorbing  liquid  through 
the  tube  d,  which  is  then  closed  by  a  rubber  cork.  Into  one 
of  the  lateral  necks  enters  a  pipe  a,  drawn  out  to  a  point  and 
bent  at  the  end,  or  provided  with  a  number  of  pinhole  outlets, 
and  closed  on  the  outside  by  the  pinchcock  m.  Through  the 
cork  of  A  passes  also  the  outlet  e,  which  is  connected  by/  with 
the  aspirating  bottle  B.  Tube  g  goes  to  the  bottom  of  B  and 
on  the  outside  is  connected  with  the  rubber  tube  //,  with  pinch- 
cock  i.  Underneath  this  a  glass  jar  C  is  placed,  holding  half 
a  litre  and  divided  into  cubic  centimetres. 

The  absorbing  vessel  is  filled  rather  more  than  half,  the 
aspirator  B  entirely  with  water ;  all  corks  are  put  in  tightly, 
the  pinchcock  m  is  closed  and  the  apparatus  is  tested  for 
tightness  by  opening  tap  i.  The  flow  of  water,  which  at  first 
is  continuous,  should  soon  change  into  slow  dropping  and  at 
last  cease  entirely,  if  there  is  no  leakage  in  the  apparatus. 


138 


TECHNICAL  GAS-ANALYSIS 


FIG.  69. 


APPARATUS  OF  REICH-LUNGE  139 

A  suitable  volume  of  absorbing  liquid  is  now  run  into  A  by 
means  of  a  pipette;  if  necessary,  also  an  indicator,  and  the 
central  neck  is  again  tightly  closed. 

The  inlet-pipe  is  now  filled  up  to  the  pinchcock  m  by  means 
of  a  small  india-rubber  pump,  and  water  is  run  off  through 
tap  i  until  the  liquid  in  the  inlet-pipe  has  just  been  forced 
down  to  its  point,  or  until  a  single  bubble  of  gas  has  come  out, 
in  order  to  bring  the  air  contained  in  A  to  the  same  pressure 
as  that  prevailing  during  the  test.  The  jar  C  is  emptied  and 
again  put  under  the  aspirator. 

Now  the  inlet-pipe  b  is  connected  with  the  source  of  the 
gas  to  be  tested,  pinchcock  m  is  opened  entirely,  and  after  this 
tap  i  so  far  that  the  gas  is  just  drawn  into  A.  It  is  thus  passed 
through  A  in  a  slow  stream,  shaking  this  bottle  from  time  to 
time,  until  the  indicator  shows  that  the  absorbent  is  saturated 
with  the  constituent  to  be  determined.  At  this  moment  both 
taps  are  closed,  and  the  test  is  complete.  Of  course  another 
test  may  follow  immediately,  after  adding  a  fresh  quantity  of 
absorbent.  The  bottle  A  needs  only  after  a  series  of  tests 
emptying,  cleaning,  and  refilling. 

The  volume  of  water  run  into  C  at  each  test  is  that  of  the 
residual  gas  ;  that  of  the  absorbed  gas  follows  from  the  quantity 
and  strength  of  the  absorbing-solution  employed.  The  calcula- 
tion is  made  as  follows: — If  we  call  the  volume  of  the  employed 
normal  solution  n  c.c.,  that  of  water  run  out  during  the  test 
m  c.c.,  there  would  be,  apart  from  all  the  corrections  : 

«  =  the  volume  of  the  gaseous  constituent  absorbed; 

7#  =  the  unabsorbed  residue  of  gas; 

#  +  ;;/  =  the  total  volume  of  gas  employed  in  the  test 

The  percentage  (by  volume)  of  the  constituent  found  by 
titration  to  the  total  volume  of  the  gas  tested  is  : 

10071 

n  +  m' 

For  accurate  estimations  we  have  to  consider  that  n  means 
a  corrected,  ;//  an  uncorrected  volume  of  gas.  Hence,  in  order 
to  get  an  accurate  result,  m  must  be  corrected  in  the  manner 
explained  supra,  pp.  17  et  seq.,  or  by  the  mechanical  apparatus 
described  p.  19. 

This  proceeding  will  be  made  clearer  by  describing  in  detail 


140 


TECHNICAL  GAS-ANALYSIS 


the  operation  for  which  Reich's  apparatus  was  intended  in  the 
first  place,  viz.,  the  estimation  of  sulphur  dioxide  in  pyrites-kiln 
gases.  Add  a  little  clear  starch  solution  to  the  water  contained 
in  the  absorbing  bottle  A  ;  by  means  of  a  pipette  put  in  a 
suitable  quantity  of  decinormal  iodine  solution,  say  10  c.c.,  and 
draw  the  gas  to  be  tested  through  the  liquid  until  the  blue 
colour  has  been  almost,  but  not  entirely,  destroyed.  It  is  not 
advisable  to  go  up  the  entire  decolorisation  of  the  liquid, 
because  thereby  the  experiment  is  very  easily  overdone; 
should  this  have  happened,  the  liquid  must  be  coloured  faintly 
blue  by  adding  one  or  more  drops  of  iodine  solution  before 
commencing  a  new  test.  When  testing  gases  containing  but 
little  SO2,  it  is  advisable  to  add  a  little  sodium  carbonate  to  the 
absorbing  liquid  ;  but  in  this  case  bottle  A  must  be  freshly 
charged  each  time,  because  otherwise  CO2  would  be  given  off 
and  would  cause  an  error  by  increasing  the  volume  of  the 
unabsorbed  gas. 

The  calculation  is  made  as  follows  :  —  Since  the  reaction  is  : 

2,  the  10  c.c.  decinormal  iodine 


solution  (  =  0-12692  g.  I)  correspond  to  0-032035  g.  SO2.  This 
is  =10-95  c.c.  SO2  at  o°  and  760  mm.  Suppose  that  128  c.c. 
water  has  run  out,  this  is  equal  to  the  same  volume  of  gas  not 
absorbed  by  iodine  solution.  Hence  there  was  present  : 


10.95 


I38-95 


=    7.88  voiume  per  cent.  SO.,. 


The  following  table  makes  this  calculation  unnecessary  :  — 


c.c.  of  water 
run  out. 

Vol.  per  cent. 
SO2  in  the  gas. 

c.c.  of  water 
run  out. 

Vol.  per  cent. 
SO2  in  the  gas. 

80-3 

120 

126-0 

8-0 

84-3 

ii-5 

135-1 

7-5 

88-6 

11-0 

145-5 

7-0 

93-4 

10-5 

157-6 

6-5 

98-6 

IO-O 

171-6 

6.0 

104-4 

9-5 

188.2 

5-5 

1  10-8 

9-0 

208-1 

5-0 

117.9 

8-5 

N.B. — When  using  this  table,  the  10-95  c*c«  corresponding  to  the  iodine  consumed 
must  not  be  added  to  the  volume  of  the  water  run  out. 

In   the   calculation    as   described,   no   regard    is   taken   of 
temperature  and  barometric  pressure.     If  this  is  to  be  done, 


APPARATUS  OF  REICH-LUNGE  141 

the  volume  read  off  must  be  reduced  to  o°  and  760  mm.  as 
above  mentioned.  If  this  correction  is  neglected,  considerable 
errors,  of  10  per  cent,  and  upwards,  will  be  caused  in  this 
calculation  if  the  test  is  taken  at  somewhat  high  temperatures 
and  low  barometric  pressures. 

Reich's  method  has  been  applied  by  Lunge  (Z.  angew.  Chem., 
1890,  563)  to  the  estimation  of  total  acids  in  pyrites-kiln  gases 
and  analogous  gases.  Since  these  gases  always  contain  some, 
and  may  contain  a  considerable  proportion  of  sulphur  trioxide 
which  is  not  indicated  by  the  iodometrical  estimation,  it  is 
preferable  to  express  the  value  of  such  gases  by  their  percentage 
of  total  acids ',  i.e.  SO2  +  SO3.  In  such  cases  the  best  absorbent 
is  a  standard  solution  of  potassium  or  sodium  hydroxide,  of 
which  a  suitable  quantity  is  put  into  the  bottle  A,  Fig.  69  (or 
into  the  bottles  specially  employed  for  this  purpose  by  Lunge 
and  others,  which  will  be  described  later  on).  The  indicator  in 
this  case  is  an  alcoholic  solution  of  phenolphthalein  (i  :  1000), 
of  which  a  few  drops  are  added,  sufficient  to  give  to  the  liquid 
a  vivid  red  colour.  The  gas  is  not  drawn  through  it  continu- 
ously, but  in  small  portions  at  a  time,  agitating  each  time  about 
half  a  minute.  Any  arsenious  acid  carried  along  by  the  gas  is 
kept  out  by  interposing  a  small  glass  tube  filled  with  asbestos. 
The  operation  is  finished  when  the  last  pink  shade  has  vanished, 
which  is  easily  noticed  even  in  the  dusk  or  when  employing 
artificial  light  by  employing  a  white  paper  as  background.  At 
this  point  normal  sulphite  and  sulphate  (Na2SO3  and  Na2SO4) 
are  formed.  Other  indicators,  e.g.  litmus,  are  not  admissible,  as 
they  yield  different  results  for  sulphurous  and  sulphuric  acid. 

If  HC1  is  present  as  well,  it  can  be  estimated  in  the  liquid, 
after  titrating  for  total  acids  as  just  described,  by  Volhard's 
method  (titration  with  silver  nitrate  and  retitrating  with 
ammonium  sulphocyanide). 

The  Reich  apparatus  is  employed  by  Raschig  (Z.  angew. 
Chem.,  1909,  xxii.  p.  1182)  for  estimating  in  vitriol-chamber 
gases  both  sulphur  dioxide  and  nitrous  gases,  by  charging  it 
with  10  c.c.  of  decinormal  iodine  solution,  about  100  c.c.  water, 
a  little  starch  solution,  and  10  c.c.  of  a  cold  saturated  solution 
of  sodium  acetate.  The  chamber  gases  are  passed  through, 
taking  care  that  no  droplets  of  sulphuric  acid  get  into  the 
iodine  solution,  which  is  prevented  by  a  glass-wool  filter.  The 


142  TECHNICAL  GAS-ANALYSIS 

calculation  of  the  sulphur  dioxide  is  carried  out  as  stated  supra, 
p.  no.  In  order  to  estimate  the  nitrous  gases,  a  drop  of 
phenolphthalein  is  now  added  to  the  decolorised  liquid  and 
decinormal  caustic  soda  solution  is  added  until  a  pink  colour 
appears.  From  the  number  of  cubic  centimetres  of  soda  solution 
required  for  this,  10  c.c.  is  deducted  for  HI  and  loc.c.  for  the 
sulphuric  acid  formed  by  the  reaction  : 

S02+I2+2H2O  =  H2S04+2HI. 

The  decinormal  soda  solution  required  in  excess  of  these  20  c.c. 
indicates  the  nitric  or  nitrous  acid  present. 

The  same  apparatus  can  be  used  for  estimating  the  sulphur 
trioxide  formed  by  the  passage  of  burner-gases  through  contact 
apparatus.  The  catalysed  gases  are  passed  through  a  measured 
quantity  of  iodine  solution,  where  the  SO2  is  oxidised  to 
H2SO4.  The  iodine  left  in  the  free  state  is  determined  by 
thiosulphate  solution,  and  the  total  acidity  by  baryta  or 
decinormal  soda  solution  and  phenolphthalein,  making  the  same 
deduction  of  acid  as  in  the  Reich-Raschig  method  (p.  no).  If 
the  cubic  centimetres  of  decinormal  iodine  solution  consumed  are 
called  a,  and  those  of  decinormal  soda  (or  baryta)  =  b,  the  quantity 
of  uncatalysed  SO2  is  :x=  0-0032  a  g.  and  that  of  SO3  formed  : 
y  —  0-004  (b  —  2a).  The  yield  of  SO3  in  per  cent,  by  volume  is  : 

(b-  20)100 
b-a 

A  modification  of  the  Reich  apparatus,  constructed  by  Rabe, 
is  sold  by  H.  Gockel,  Berlin  N.W.  6. 

3.  The  Minimetric  Method. — This  method  was  in  the  first 
instance  indicated  by  R.  Angus  Smith,  who  applied  it  to  the 
approximate  estimation  of  carbon  dioxide  in  air,  by  producing, 
as  final  reaction,  a  certain  just  visible  degree  of  turbidity  in  the 
absorbing  liquid,  which  consisted  in  a  solution  of  lime  or  baryta 
in  water.  I  myself  also  employed  this  method  (Lunge,  Zur 
Frage  der  Ventilation,  1877),  but  I  soon  rejected  it  in  its 
original  shape,  because  the  final  reaction  is  too  uncertain,  and 
varies  too  much  according  to  the  degree  of  light  in  the  locality. 
I  therefore  worked  out  another  method  based  on  titration,  with 
the  assistance  of  Zeckendorf  (Z.  angew.  Chem.,  1888,  pp.  395 
et  seq.\  which  will  now  be  described.  Fig.  70  shows  the  apparatus 
employed.  The  bottle  A  (which  may  also  have  a  conical  shape) 
holds  about  150  c.c.  (the  exact  contents  being  marked  on  it)  and 


LUNGE  AND  ZECKENDORF'S  METHOD 


143 


receives  a  measured  quantity  of  the  absorbent  to  be  employed. 
Through  its  doubly  perforated  rubber  cork,  which  reaches 
down  to  a  mark  in  the  neck  of  A,  passes  an  inlet-pipe,  ending 
just  below  the  cork,  and  an  outlet-pipe,  connected  by  strong 
rubber  tubing  with  the  india-rubber  ball  or  "  finger-pump  "  B. 
This  pear-shaped  ball  is  provided  with  clack-valves,  and  at  each 
compression  by  the  hand  of  the  operator  delivers  about  70  c.c. ; 
the  quantity  to  be  ascertained  by  a  number  of  trials. 

In  making  a  test,  the  bottle  A  is  first 
left  empty.  Then  the  bulb  B  is  firmly 
compressed  with  the  right  hand,  and 
allowed  to  expand  again,  whereby  it  is 
filled  with  the  air  of  the  space  to  be 
examined  ;  this  is  best  repeated  a  few 
times.  Now  the  bottle  A  is  opened, 
10  c.c.  of  the  reagent  is  quickly  run  in 
from  a  pipette,  the  cork  is  at  once  put 
on  and  the  air  contained  in  bulb  B  is 
slowly  pressed  in  by  squeezing  the  bulb, 
shaking  B  with  the  other  hand.  This 
agitation  is  continued  for  another 
minute,  taking  care  that  the  whole  gas- 
eous contents  of  A  come  into  contact 
with  the  liquid.  This  liquid  in  testing 
air  for  CO2* consists  of  a  72/500  solution 
of  sodium  carbonate  (here  the  term 
"normal"  =  n  is  understood  in  the 
ordinary,  not  the  gas-volumetric  sense), 
coloured  red  by  dissolving  0-02  g.  phenol- 
phthalein  in  a  litre  of  it.  The  colour  of  this  solution  gradually 
turns  paler,  as  more  and  more  bulb-fillings  are  forced  through 
and  out ;  in  perfectly  pure  air  of  woods  or  fields  more  than 
forty  bulbsfull  would  be  required  for  discharging  it;  in  the  air  of 
ordinary  living-rooms,  about  nine  or  ten  bulbs  ;  in  strongly  con- 
taminated air,  correspondingly  less,  down  to  two  or  three  bulbs- 
full.  The  pink  colour  is  destroyed  and  turned  into  light  yellow, 
when  all  the  Na2CO3  has  been  converted  into  NaHCO3,  and  a 
trace  of  free  CO2  is  superadded. 

The  above-mentioned  sodium  carbonate  solution  (72/500  = 
0-0106  g.  Na2CO3  per  litre)  must  not  be  kept  for  any  length  of 


FIG.  70. 


144 


TECHNICAL  GAS-ANALYSIS 


time  in  half-filled  or  not  tightly  closed  vessels,  as  it  is  spoilt 
already  in  a  few  hours  by  the  action  of  the  CO2  in  the  air  of  the 
room.  It  is  therefore  preferable  to  keep  only  a  decinormal 
solution  (=  5-3  g.  Na2CO3  per  litre)  in  stock,  which  is  coloured 
red  by  I  g.  phenolphthalein  (dissolved  in  alcohol)  per  litre. 
Before  actual  use,  2  c.c.  of  this  njio  solution  is  diluted  with 
distilled,  freshly  boiled  (and  cooled)  water  to  100  c.c.,  and  of 
this  72/500  solution,  which  must  have  still  a  strongly  red  colour, 
10  c.c.  is  used  for  each  test.  In  between  the  100  c.c.  flask  is 
kept  well  closed,  and  if  the  experiments  have  to  be  interrupted 
for  several  days,  the  dilute  solution  is  thrown  away. 

Special  experiments  showed  that  the  n/io  solution  keeps 
equally  well  in  bottles  of  ordinary  glass  and  in  Bohemian 
potash  glass. 

Of  course  the  quantity  of  air  originally  present  in  the  bottle 
A  also  contributes  to  the  result,  but  as  this  magnitude  is 
constant,  it  can  be  neglected  in  drawing  up  the  empirical  table 
to  be  just  mentioned. 

The  CO2  present  in  the  air  tested  cannot  be  simply 
calculated  from  the  number  of  bulb-fillings  required  for 
decolorising  the  10  c.c.  of  72/500  solution  ;  it  is  always  consider- 
ably higher,  and  all  the  more  so  the  purer  the  air.  Various 
reasons  contribute  to  this  result,  more  particularly  the  fact  that 
a  little  CO2  is  expelled  from  the  Na2CO3  solution  by  mere 
prolonged  shaking  with  air  free  from  CO2.  In  order  to 
establish  the  real  relation  between  the  number  of  bulb-fillings 
required  in  the  test,  and  the  actual  percentage  of  CO2  in  the 
air,  Lunge  and  Zeckendorf  made  a  prolonged  series  of  experi- 
ments with  all  possible  precautions,  which  led  them  to  draw  up 
the  following  table  : — 


Number  of 
bulb-fillings. 

CO2  in  air. 
Per  cent,  by 
vol. 

Number  of 
bulb-nllings. 

CO2  iu  air. 
Per  cent,  by 
vol. 

Number  of 
bulb-fillings. 

CO-2  in  air. 
Per  cent,  by 
vol. 

2 

0-300 

II 

0-087 

20 

0-062 

3 

0-250 

12 

0-083 

22 

0-058 

4 

0-210 

13 

0-080 

24 

0-054 

5 

0-180 

14 

0-077 

26 

0-051 

6 

0-155 

15 

0-074 

28 

0-049 

7 

0-135 

16 

0-071 

30 

0-048 

8 

0-115 

17 

0-069 

35 

0-042 

9 

0-100 

18 

0-066 

40 

0-038 

10 

0-090 

19 

0-064 

WINKLER'S  ABSORPTION  COIL  145 

Fuchs  (quoted  by  Lehmann,  Prakt.  Hygiene,  1900,  p.  149) 
has  found  these  empirically  established  results  to  be  correct, 
but  he  prefers  employing  a  solution  of  twice  the  strength,  z>., 
4  c.c.  of  the  n/io  solution  diluted  to  100  c.c.  His  results  agree 
to  about  one-tenth  of  their  value. 

This  apparatus  can  be  also  used  for  estimating  the  small 
quantities  of  hydrogen  chloride  in  the  air  of  alkali  works,  etc., 
employing  a  decinormal  solution  of  potassium  hydrate  as 
absorbent,  with  methyl  orange  as  indicator ;  or  the  total  acids 
in  acid-smoke,  etc.,  with  potash  solution  and  methyl  orange 
(as  described  p.  141),  or  the  sulphur  dioxide  in  chimney-gases, 
etc.,  with  iodine  solution  and  starch. 


FIG.  71. 

4.  Various  Apparatus  for  estimating  Gaseous  Constituents 
occurring  in  Minute  Quantities. — In  these,  as  in  the  preceding 
cases,  the  gas  should  be  brought  into  intimate  contact  with 
the  absorbent,  frequently  during  a  certain  length  of  time.  Of 
the  numerous  apparatus  constructed  for  this  purpose  we  describe 
the  following : — 

i.  Winkler 's  Absorption  Coil  (Fig.  71)  consists  of  a  spiral 
glass  tube  A,  resting  on  three  glass  feet,  and  filled  with  the 
absorbing  liquid  nearly  up  to  the  bulb  E.  Into  its  bottom  is 
sealed  the  inlet-tube  B,  provided  with  a  bulb  D  and  a  pointed 
end  F.  From  the  latter  the  gas  entering  at  C  issues  in  small 
bubbles,  like  a  string  of  beads  travelling  upwards  singly  in  the 
coil  A,  and  leaving  it  after  a  comparatively  long  time  at  Cx. 

K 


146  TECHNICAL  GAS-ANALYSIS 

The  gradient  of  the  wall  must  be  gentle  and  quite  uniform ; 
otherwise  the  small  bubbles  unite  into  large  ones,  which  should 
be  avoided,  because  there  is  then  too  little  contact  between 
the  gas  and  the  liquids.  Many  of  the  coils  found  in  trade  do 
not  fulfil  this  requirement;  we  therefore  quote  suitable 
dimensions  for  two  different  sizes  of  coils  (in  millimetres) : — 

Size  1.  Size  2. 

Width  of  A  .  .  .  .  22-0  7-5 

„  B  .  •  .  .  .'  10-0  4-5 

„  CandCi.  '  .  -  .  .  -  6-5  4-5 

Diameter  of  bulb  D  -.-  .  .  35-0  15-0 

„  E  ,.:  .  .  60-0  30-0 

Diameter  of  coil  A  .  • ;  .  200-0  80-0 

Height  from  foot  to  bulb  E  .  .  170-0  80-0 

Properly  made  absorption  coils  do  excellent  service, 
especially  in  such  cases  where  the  object  is  less  the  estima- 
tion than  the  complete  removal  of  a  gaseous  constituent,  e.g. 
carbon  dioxide  from  atmospheric  air,  for  which  purpose  size  i 
is  most  suitable. 

Kyll  (Chem.  Zeit.>  1896,  p.  1006)  describes  a  modification  of 
this  apparatus. 

2.  Lunge's  Ten-bulb  Tube  (Z.  angew.  Chem.,  1890,  p.  567), 
Fig.  72,  has  a  very  good  effect,  superior  to  most  other  apparatus 


FIG.  72. 

of  this  kind,  when  the  constituent  in  question  is  to  be  estimated 
either  volumetrically  or  gravimetrically,  because  the  gas-bubbles 
are  constantly  broken  up  again.  The  large  bulb  in  the  entrance 
tube  prevents  the  liquid  from  being  forced  back  by  atmospheric 
pressure. 


ESTIMATION  BY  WEIGHT 


147 


3.    Volhard's  Absorbing  Flask,  Fig.  73  (Volhard,  Ann.  Chem., 
clxxvi.  p.  282),  improved  by  Fresenius  (Z.  anal.  Chem.,  1875, 


FIG.  73- 

P-  332)  by  the  addition  of  another  bulb  in  the  lateral  tube. 
They  are  mostly  made  about  II  cm.  high,  7  cm.  wide  at  the 
bottom,  and  2-5  cm.  wide  at  the  top,  and  are  charged  with  from 
25  to  50  c.c.  of  liquid,  which  by  the  pressure  of  the  gas  is 
partially  forced  up  into  the  lateral  tube.  After  finishing  the 
absorption,  the  liquid  can  be  titrated  in  the  flask  itself. 

4.  Drehschmidf.s  Absorbing  Cylinder,  Fig.  74.— The  central 
tube,  passing  through  the  rubber  cork,  ends  at  the  bottom  in 
a  closed  glass  bulb,  with  pin  holes  in  the  upper 
part,  by  which  the  gas  is  divided  into  very  small 
bubbles. 

C.— ESTIMATION  OF  GASES  BY  WEIGHT. 

The  estimation  of  gases  by  weight  is  ex- 
ceptionally performed  in  such  cases  where  the 
constituent  in  question  is  only  present  in  very 
slight  quantity,  and  where  we  possess  no 
convenient  volumetric  methods  for  the  purpose. 

The  gases  are  for  this  purpose  passed 
through  absorbing  apparatus  of  the  same  kind 
as  those  described  supra  for  the  estimation  by 
titration,  pp.  132  et  seq.,  and  the  calculation  of 
the  results  is  made  in  the  way  as  described  there. 

We  here  mention  some  applications  of  this  method. 

I.  Estimation  of  Hydrogen  Sulphide,  Carbon  Bisulphide,  and 
Acetylene  in  Coal-gas. — The  gas,  before  entering  the  meter  or 
the  aspirator  where  it  is  to  be  measured,  passes  through  two 
Volhard's  absorbing  flasks,  vide  supra,  each  of  them  containing 
25  c.c.  of  a  concentrated  ammoniacal  solution  of  silver  nitrate, 
then  through  a  combustion  tube  of  about  25  cm.  length,  filled 


FIG.  74. 


148  TECHNICAL  GAS-ANALYSIS 

with  platinised  asbestos  (the  preparation  of  which  will  be 
described  later  on,  and  heated  to  an  incipient  dark  red  heat  ; 
finally  again  through  two  Volhard's  flasks,  each  of  them 
charged  with  20  c.c.  of  ammoniacal  silver  solution.  To  make 
quite  sure,  three  such  flasks  instead  of  two  may  be  employed 
before  and  behind  the  combustion  tube.  For  each  test  100 
litres  of  gas  are  employed,  and  from  ten  to  twelve  hours  should 
be  allowed  for  passing  them  through  the  apparatus. 

The  contents  of  the  receivers  placed  in  front  of  the 
combustion  tube  after  some  time  show  a  whitish,  then  a  darker 
turbidity,  caused  by  the  precipitation  of  the  silver  compounds 
of  hydrogen  sulphide  and  acetylene  which  are  absorbed  there. 

The  carbon  disulphide  and  other  sulphur  compounds  present 
in  coal-gas,  on  passing  through  the  combustion  tube  and  coming 
in  contact  with  the  hot  platinised  asbestos,  form  hydrogen 
sulphide,  which  is  absorbed  in  the  following  receivers,  and 
causes  there  a  blackish  brown  precipitate  of  silver  sulphide. 

After  finishing  the  operation,  the  contents  of  the  receivers 
in  front  of  the  combustion  tube  are  united,  and  also  those  of 
the  receivers  behind  the  tube.  They  are  separately  passed 
through  filters,  and  the  precipitates  are  carefully  washed.  The 
precipitate  from  the  front  receivers  is  cautiously  covered  on 
the  filter  with  dilute  hydrochloric  acid,  keeping  the  funnel 
covered  with  a  watch-glass.  This  causes  the  silver  acetylide 
to  decompose  into  gaseous  acetylene,  which  escapes  with  slight 
effervescence,  and  silver  chloride,  which  remains  mixed  with 
the  silver  sulphide.  After  washing  the  mass  on  the  filter  with 
water,  the  silver  chloride  is  extracted  by  dilute  ammonia, 
reprecipitated  from  the  filtrate  by  saturating  this  with  nitric 
acid,  and  then  dried  and  weighed  in  the  usual  manner.  From 
the  weight  of  this  silver  chloride  that  of  the  acetylene  originally 
present  in  the  coal-gas  can  be  deduced  by  means  of  the 
following  formula  (founded  on  the  research  of  E.  K.  Keiser, 
Amer.  Chem.  J.>  xiv.  p.  285): 

=   2AgCl  +  C2H2. 


That  means  that  I  g.  AgCl  corresponds  to  0-09072  g.  acetylene 
=  84-03  c.c.  at  760  mm.  and  15°  C.  in  the  moist  state. 

On  the  filter,  after  extracting  the  silver  chloride,  only  silver 
sulphide    remains,    corresponding    to    the    hydrogen    sulphide 


ESTIMATION  BY  WEIGHT  149 

originally  present  in  the  coal-gas.  After  burning  the  filter, 
the  Ag2S  can  be  immediately  converted  into  metallic  silver 
by  heating  it  in  a  current  of  hydrogen.  One  g.  of  silver  found 
in  this  way  corresponds  to  0-1486  g.  S,  or  0-1579  g-  H2S,  or 
103-78  c.c.  H2S  of  760  mm.  pressure  and  oe  C.  in  the  original  gas. 

The  silver  sulphide  precipitated  in  the  receivers  placed 
behind  the  combustion  tube  has  been  produced  from  the  other 
sulphur  compounds  present  in  coal-gas,  such  as  carbon 
disulphide^  phenyl  sulp  ho  cyanide^  etc.  It  is  equally  converted 
by  the  just-described  process  into  metallic  silver,  which  is 
weighed  and  calculated  as  carbon  disulphide^  since  this  compound 
is  always  predominant.  One  g.  of  silver  =  0-1486  g.  S  corre- 
sponds to  0-1764  g.  C'S2,  or  52-12  c.c.  of  vapour  of  CS2  at  760 
mm.  pressure  and  o°  C. 

It  is  not  usual  to  express  the  percentage  of  H2S  and  GS2 
in  coal-gas  by  volumes,  or  by  weight,  but  generally  only  the 
number  of  grammes  of  sulphur  contained  in  100  cb.m.  (in 
England  grains  per  cubic  foot ;  I  g.  per  cubic  metre  =  0-4372  gr. 
per  cubic  foot)  is  indicated  as  the  total  sulphur  contained  in 
the  gas.  This  is  generally  estimated  by  burning  a  known 
volume  of  the  gas  and  receiving  the  products  of  combustion 
in  a  solution  of  potassium  carbonate  containing  a  little  bromine, 
from  which  solution  the  sulphuric  acid  formed  is  precipitated 
by  barium  chloride.  One  g.  BaSO4  =  0-1373  g.  S.  Special 
apparatus  for  this  purpose  have  been  described  by  Drehschmidt 
(Chem.  Zeit.,  1887,  p.  1382)  and  by  F.  Fischer  (Z.  angew.  Chem., 
1897,  p.  302).  Since  those  gases  occur  in  coal-gas  merely  in 
minute  quantities,  their  volumes  need  not  be  counted  when 
calculating  the  results,  the  unabsorbed  gas  measured  in  the 
meter  or  aspirator  being  assumed  as  equal  to  the  total  volume 
of  gas  tested. 

The  calculation  of  the  results  will  be  made  clearer  by 
giving  an  example  of  a  special  case. 

State  of  barometer,  733  mm.;  thermometer,  18°  C. 

Volume  of  gas  employed,  107  litres. 

Corrected  for  760  mm.  and  o°,  94-787  litres. 

Found  by  weighing : 

AgCl  =  0-3190  g.  =  24.92  c.c.  acetylene. 
Aga     =  o-oni  „    =     1.15    „    hydrogen  sulphide. 
=  0-3888  „    =  20-26    „    carbon  disulphide. 


150  TECHNICAL  GAS-ANALYSIS 

Total  sulphur : 

Ag<2  =  o-oni  g.  =  0-001647  g-  S 
Agt>  =  0-3888  „  =  0-057765  g.  S 
0-059412 

100  cb.m.  of  gas  contain  62-68  g.  sulphur. 
Expressed  in  per  cent,  by  volume  : 

Acetylene  .  .  .        0-02629  per  cent. 

Hydrogen  sulphide          ,  .        0-00121        „ 

Carbon  disulphide  .  .        0-02126       „ 

2.  Estimation  of  Sulphuretted  and  Phosphoretted  Hydrogen  in 
Crude  Acetylene. — The  sulphur  in  technical  acetylene  gas  exists 
mostly  in  the  shape  of  organic  sulphur  compounds,  which  have 
been  separated  from  it  by  Knorre  and  Arendt  (  Verh.  Gewerbfleiss, 
1900,  p.  155).  It  is,  however,  admissible  to  express  them  in 
terms  of  H2S,  or  else  in  grammes  S  per  cubic  metre. 

Lunge  and  Cedercreutz  (Z.  angew.  Chem.,  1897,  p.  651)  have 
described  the  following  process  for  estimating  both  these 
impurities  at  the  same  time : — A  known  volume  of  gas  is 
slowly  passed  through  a  ten-bulb  tube  (p.  146),  charged  with  a 
2  or  3  per  cent,  solution  of  sodium  hypochlorite.  The  liquid 
is  washed  into  a  graduated  flask,  and  in  one  half  of  it  the 
sulphuric  acid  is  gravimetrically  estimated  as  barium  sulphate 
(i  g.  BaS04  =  o.i373  g.  8  =  01459  g.  H2S  =  95-86  c.c.  H2S);  in 
the  other  half  the  phosphoric  acid  is  estimated  as  magnesium 
pyrophosphate  (i  g.  Mg2P2O7  =  0-2784  g.  P  =  0-305 5  g.  H3P  = 
200-91  c.c.  H3P). 

Dennis  and  O'Brien  (/.  Ind.  and  Eng.  Chem.,  1912,  No.  u, 
Nov.)  propose  to  improve  this  method,  first,  by  evolving  the 
acetylene  from  the  calcium  carbide  without  marked  rise  of 
temperature  in  a  small  Kipp  apparatus  by  means  of  a  saturated 
solution  of  sodium  chloride ;  secondly,  by  employing  as  absorp- 
tion apparatus  a  Friedrichs  gas-washing  bottle,  modified  so  that 
the  apparatus  can  be  easily  rinsed  out  with  water  at  the  close. 

3.  Detection  and  Approximate  Estimation  of  Very  Small 
Quantities  of  Sulphur  Dioxide  and  Sulphuric  Acid  in  Air> 
suspected  of  being  contaminated  by  Acid-smoke. — Ost  (Chem.  Zeit.y 
1896,  p.  170)  and  H.  Wislicenus  {Z.  angew.  Chem.,  1901,  p. 
689)  chemically  fix  the  acid  contained  in  the  suspected  air  of 


ESTIMATION  BY  COMBUSTION  151 

forests,  etc.,  by  exposing  to  it  during  a  long  time  wooden  frames, 
of  a  superficial  area  of  I  sq.  m.,  covered  with  loose  cotton  tissue, 
impregnated  with  barium  carbonate  by  moistening  with  baryta 
water.  This  gives  an  idea  of  the  quantity  of  soot  present,  and 
later  on  by  incineration  and  estimation  of  the  sulphate  contained 
in  the  ash  shows  the  quantity  of  the  acids  of  sulphur  present  in 
the  air. 

For  the  conclusions  to  be  drawn  from  this  process  (which  is 
not  yet  fully  worked  out)  we  must  refer  to  the  originals. 

Cf.  also  the  description  in  Lunge-Keane's  Techn.  Methods^ 
\.  pp.  384  et  seq. 

III.  ESTIMATION  OF  GASES  BY  COMBUSTION. 

General  Observations. 

A  number  of  gases,  especially  of  those  which  cannot  be 
estimated  by  physical  or  chemical  absorption,  can  be  transformed 
by  combustion  with  oxygen  into  compounds  which  admit  of 
determination,  either  by  the  contraction  of  volume  caused  by 
their  condensation  to  the  liquid  state,  or  by  absorption  by 
chemical  reagents.  The  former  takes  place  by  the  formation  of 
water  from  hydrogen  or  compounds  containing  this  in  chemical 
combination,  the  latter  principally  by  the  formation  of  carbon 
dioxide. 

The  oxygen  required  for  combustion  is  sometimes  already 
contained  in  the  gaseous  mixture  to  be  analysed.  If  not,  it  is 
in  technical  analysis  usually  added  in  the  shape  of  atmospheric 
air,  only  exceptionally  in  that  of  pure  oxygen,  and  in  both  cases 
in  reasonable  excess  of  that  which  is  required  for  complete 
combustion.  A  suitable  mixture  having  been  prepared,  the 
combustion  is  effected  either  suddenly  by  explosion,  or  slowly 
by  passing  the  mixture  over  a  heated  number  of  the  platinum 
group.  Hereby  the  hydrogen,  both  that  present  in  the  free 
state  and  that  existing  in  the  shape  of  hydrocarbons,  is 
transformed  into  water,  which  on  cooling  separates  in  the  liquid 
state;  the  carbon  is  transformed  into  carbon  dioxide,  which 
is  estimated  by  absorption  with  caustic  alkali  in  the  usual 
manner. 

Changes  of  Volume  by  the  Combustion  and  Calculation  of  the 


152  TECHNICAL  GAS-ANALYSIS 

Single  Combustible  Gases.1 — We  need  here  consider  only  three 
gases :  hydrogen,  methane,  and  carbon  monoxide.  The  other 
combustible  gases,  all  of  them  hydrogen  compounds,  are  more 
suitably  previously  taken  out  by  absorption,  as  described  on 
pp.  117  et  seq.  Usually  this  is  also  done  with  carbon  monoxide 
(cf.  pp.  126  et  seq.\  but  sometimes  it  is  more  convenient  to 
estimate  this  by  combustion. 

The  above-mentioned  three  gases,  when  burned,  produce 
the  following  changes  of  volume  : — 

Hydrogen. — 2  vols.  H2  +  I  vol.  O  yield  water,  H2O,  which 
completely  condenses  on  cooling,  thus  causing  a  contraction  of 
the  volume,  two-thirds  of  which  correspond  to  the  hydrogen 
originally  present. 

Methane.  —  The  reaction  is:  CH4  +  2O2  =  CO2  +  2H2O. 
Hence  2  vols.  CH4-f  4  vols.  O  =  6  vols.  on  combustion  yield  2 
vols.  CO2,  the  water  being  removed  from  the  gas  in  the  liquid 
state.  The  contraction  occurring  on  combustion  is  therefore : 
6  —  2  vols.  =  4  vols.,  half  of  which  =  2  vols.,  represents  the 
originally  present  methane,  whose  volume  is  therefore  equal  to 
half  of  the  contraction  caused  by  the  combustion,  or,  if  the 
carbon  dioxide  is  removed  by  absorption,  to  one-third  of  the 
total  contraction. 

Carbon  Monoxide. — 2  vols.  CO-f-i  vol.  O2  =  3  vols.  of  the 
mixture  yield  2  vols.  CO2 ;  hence  two-thirds  of  the  contraction 
represent  the  carbon  monoxide.  Or,  if  we  remove  the  CO2  by 
absorption,  the  carbon  monoxide  is  equal  to  one-third  of  the 
total  contraction. 

Oxygen  can  be  estimated  in  a  gaseous  mixture  by  adding  a 
measured  excess  of  hydrogen  effecting  the  combustion,  and 
calculating  the  amount  of  oxygen  from  contraction  :  O2-f2H2  = 
2H2O,  one-third  of  which  is  due  to  the  oxygen  originally 
present. 

If  only  one  of  the  combustible  gases  has  to  be  counted  with, 
we  may  for  methane  and  carbon  monoxide  choose  to  calculate 
the  original  volume,  either  from  the  contraction  after  com- 
bustion, or  from  the  carbon  dioxide  formed,  or  from  the  total 
contraction  after  absorption  of  the  carbon  dioxide.  The  last, 

1  From  the  paper  of  O.  Pfeiffer  in  Lunge  and  BerPs  Chemische-technische 
Untersuchung-methoden^  6th  ed.  (1911),  vol.  iii.  pp.  242  et  seq. 


ESTIMATION  BY  COMBUSTION  153 

which  produces  the  greatest  values  to  be  observed,  naturally 
yields  the  most  exact  results. 

The  calculation  is  more  complicated  in  case  of  mixtures  of 
two  or  all  three  of  the  combustible  gases  here  considered. 

Hydrogen  along  with  Carbon  Monoxide. — The  hydrogen  by 
itself  is  equal  to  two-thirds  of  the  contraction  produced  by  the 
combustion,  since  the  carbon  monoxide  on  combustion  yields 
its  own  volume  of  carbon  dioxide.  The  volume  of  carbon 
monoxide  originally  present  is  equal  to  that  of  the  carbon 
dioxide  formed  on  combustion,  and  found  by  the  subsequent 
absorption  of  this. 

We  illustrate  this  by  an  example  of  the  combustion  of  a 
mixture  of  hydrogen,  carbon  monoxide,  and  nitrogen. 

Gaseous  mixture  employed      .  .      21-1  c.c. 

Air  added          ,  .         .  .  .      97-5    „ 

Together        n 8-6  c.c.  employed. 

Volume  after  combustion  .  .       102-1    c.c. 

Contraction  .  .  .         16-5     „ 

H  .  .  .  •  .          9'53   » 

After  absorbing  the  CO2  .  .        97-7     „ 

CO2  formed          .  .  .4-4     „ 

CO  .  ,  .  4-4     „ 

If  hydrogen,  carbon  monoxide,  and  methane  are  all  present  in 
a  gaseous  mixture,  we  must  first  ascertain  the  total  volume  of 
the  combustible  gases,  V=  H  +  CO-f-CH4,  which  in  technical 
gaseous  mixtures  presupposes  ascertaining  the  quantity  of 
nitrogen  mixed  with  those  gases.  We  start  from  the  known 
percentage  of  nitrogen,  Nt,  in  the  air  added  for  combustion,  viz., 
N\  =  volume  of  that  air  x  0-7905.  After  accomplishing  the 
combustion,  absorbing  the  CO2  formed  and  the  excess  of 
atmospheric  oxygen,  a  nitrogen  volume  =  N2  remains,  which 
must  be  at  least  equal  to  Nr  The  difference  N2  —  Nj  shows  the 
amount  of  nitrogen  N  present  in  the  gaseous  mixture  B 
employed.  From  this  follows : — 

(a)  Combustible  Gases  V  =  R  -  N. 

(b)  Hydrogen.— Since,  on  the  other  hand,  V  =  H  +  CO  +  CH4, 
we  have 

H  =  V-(CO  +  CH4y 


154  TECHNICAL  GAS-ANALYSIS 

Since,  moreover,  the  volume  of  the  total  carbon  dioxide 
formed  on  combustion  is  equal  to  that  of  the  carbon  monoxide 
and  methane  burned:  CO2  =  CO  +  CH4,  we  may  alter  the  just 
given  equation  into — 

H  =  V-C02, 

and  we  thus  ascertain  the  volume  of  hydrogen  present. 

(c)  Carbon  Monoxide. — If  we  add  the  total  contractions  (C) 
we  get : — 

1.  C  =  JLH  +  -^-CO  =  3CH4,  and  from  this — 

2.  H  =  —  C  -  CO  -  2CH4.      Since  moreover  (vide  supra] — 

3.  V   =    H  +  CO  +  CH4,  and  therefore— 

30.  CO  =  V  -  H  -  CH4,  we  get  by  introducing  the  value  of  H  from 
equation  No.  2. 

4-      CO  =  V  -  (—  C  -  CO  -  2CH4)  -  CH4,  or 

=  V  -  —  C  +  CO  +  CH,. 
3 

Now,  as  we  have  seen  sub  b,  CO  +  CH4=CO2,  we  ultimately 
get— 

CO  m  V-  — C  +  C02. 

(d)  Methane. — According  to  the  above  equation,  No.  3 — 

CH4  -  V-H-CO. 

By  replacing  H  by  the  value  stated  supra  in  No.  2,  we  get — 
CH4  -  V-(—  C  -  CO  -  2CH4)  -  CO, 

o 

=  —  C  -  V. 
3 

(An  example  of  this  calculation  in  a  special  case  is  given 
supra>  p.  no,  when  describing  Pfeiffer's  apparatus.) 


METHODS  OF  COMBUSTION  155 

I  f  we  call— 

Vol.      I.  =  Gaseous  remainder  (R)  +  air, 
„       II.  =  Remainder  after  explosion, 

„     III.  =  „  absorbing  the  CO2  formed  in  combustion, 

„     IV.  =  „  „  oxygen  in  excess, 

we  find  therefrom  : — 

C       =  Vol.  I.-III. 
C02  =     „     II.-III. 

N2     -     „     IV. 

N       =  N2  -  Nj  (reckoning  Nx  =  Air  x  0-7905). 

V       =  R-N. 

(e)  Ethane  along  with  Methane. — Both  together  form  the 
combustible  constituent  V\  =  CH4+C2H6.  If  hydrogen  is 
present  as  well,  we  have  V^V  —  H. 

Whilst  methane  by  combustion  furnishes  its  own  volume  of 
CO2,  the  volumetric  equation  for  ethane  is — 


Hence,  if  both  hydrocarbons  are  present  (Vj),  the  combustion 
yields  a  larger  volume  of  CO2,  and  to  the  excess  corresponds 
according  to  the  just  given  equation,  an  equal  volume  of 

ethane — 

C2H6  =  C02-Vlf 

and  according  to  the  first  equation — 

/"'TT  \r  f~*    TT 

CH4  ==  Vl-L.2ti6. 

METHODS  OF  COMBUSTION. 

I. — Ordinary  Combustion. 

We  need  not  go  into  details  about  this  at  this  place,  but  we 
refer  as  an  instance  of  this  to  the  estimation  of  the  sulphur 
compounds  in  coal-gas  by  the  Drehschmidt  method,  supra, 
p.  103. 

II. — Special  Methods  of  Combustion. 

i.  By  Explosion. — The  inflammation  of  an  explosible  gaseous 
mixture,  suitably  confined,  by  the  electric  spark,  for  the  purpose 


156  TECHNICAL  GAS-ANALYSIS 

of  estimating  one  or  the  other  of  the  gases  taking  part  in  the 
explosion  by  means  of  the  subsequent  contraction,  has  been 
already  applied  by  Volta  for  the  estimation  of  oxygen  in  air 
by  means  of  his  endiometer ;  Bunsen  (Gasometriche  Methoderi) 
has  greatly  improved  and  amplified  this  method,  and  Hempel, 
as  we  have  already  seen  in  a  former  chapter  (pp.  96  et  seq.\ 
has  made  it  specially  serviceable  for  technical  gas-analysis  by 
means  of  his  "  explosion  pipettes." 

The  explosion  method  is  now  principally  applied  to  the 
estimation  by  combustion  of  hydrogen  and  of  methane.  We 
must,  however,  point  out  the  following  circumstances.  Not 
every  gaseous  mixture  containing  these  gases  and  the  requisite 
quantity  of  oxygen  can  be  straightway  brought  to  explosion  ; 
it  is  sometimes  necessary  to  add  oxyhydrogen  gas  (electro- 
lytically  produced),  or,  when  there  is  an  excess  of  oxygen 
present,  pure  hydrogen.  Nor  can  the  simultaneous  combustion 
of  a  little  nitrogen  be  always  avoided,  as  first  pointed  out  by 
Bunsen,  who  prescribes  preventing  this  by  not  employing  more 
than  from  22  to  64  vols.  of  combustion  gases  to  100  vols.  of  non- 
combustible  gases.  Pfeififer  (Lunge  and  BerPs  Untersuchungew- 
methoden,  6th  ed.,  vol.  iii.  p.  246)  in  the  analysis  of  coal-gas 
employs  22  c.c.  of  the  gases  remaining  after  the  treatment 
with  absorbing  agents  (H,  CH4,  CO,  N)  with  no  c.c.  of  air, 
which  means  about  52  vols.  combustible  gases  to  100  vols. 
non-combustible  gases. 

The  explosion  method  requires  employing  mercury  as  the 
confining  liquid.  Seger  ( Tonindustrie  Zeit.,  1878,  Nos.  25  and 
26)  has  tried  to  avoid  this  by  employing  a  special  endiometer 
with  water-seal  and  india-rubber  taps,  but  this  has  never 
become  popular.  Much  more  success  has  been  attained  by 
Hempel,  although  he  as  well  had  to  abandon  his  first  attempts 
in  that  direction.  Dennis  (Gas  Analysis^  p.  147)  describes 
a  combustion  pipette  adapted  to  mercury  as  a  confining  liquid. 
The  explosion  arrangement  has  also  been  combined  with  an 
Orsat  apparatus  by  Thorner  (Chem.  Zeit.,  1891,  p.  763),  but 
without  much  practical  application. 

The  practical  introduction  of  the  explosion  method  into 
technical  gas-analysis  is  in  the  first  instance  due  to  Hempel's 
new  arrangements  for  that  method.  We  have  already  in  a 
former  chapter  (p.  96)  described  his  new  "explosion  pipette," 


EXPLOSION  METHODS 


157 


and  we  show  his  whole  apparatus  in  Fig.  75.  The  pipette  itself 
consists  of  the  two  strong  tubulated  glass  bulbs,  a  and  £,  con- 
nected at  the  bottom  by  a  canvas-covered  rubber  tube.  The 
explosion  bulb  a  is  contracted  at  the  top,  like  an  ordinary  gas- 
pipette,  into  a  syphon-like  capillary,  closed  by  a  pinchcock  or 
glass  rod,  and  is  at  the  bottom  closed  by  a  glass  tap  ^,  which 


FIG.  75- 

is  connected  with  the  "  levelling  bulb  "  b  by  the  afore-mentioned 
rubber  tube.  At  c  two  thin  platinum  wires  are  sealed  into  the 
contracted  part  of  the  bulb  a,  leaving  a  distance  of  2  mm. 
between  their  ends,  so  that  an  induction-spark  can  pass  through. 
For  this  purpose,  the  outer  ends  of  the  platinum  wires  are 
turned  into  loops  and  are  connected  by  silk-covered  copper 
spirals  with  the  induction  apparatus  J,  which  receives  its 
current  from  the  battery  T  or  any  other  source  of  electricity. 


158 


TECHNICAL  GAS-ANALYSIS 


Both  bulbs  of  the  pipette  are  rather  more  than  half-filled  with 
mercury  ;  if  bulb  b  is  lifted,  tap  h  being  open,  a  gets  filled  with 
mercury  up  to  the  capillary,  and  is  kept  in  this  state  by  closing 
tap  h.  In  order  to  make  a  combustion,  a  suitable  quantity  of 
the  gas  to  be  burned  is  roughly  measured  off  in  the  tube  A  of 
the  Hempel  burette,  Fig.  75  ;  the  levelling  tube  B  of  the 
burette  is  placed  on  the  floor,  the  water  in  the  burette  is 
allowed  two  minutes  to  flow  down,  and  the  exact  reading  of 
the  volume  of  gas  is  now  made  by  raising  B  to  the  proper 

height.  Now  tube  B  is  again 
lowered  and  the  pinchcock  of 
A  is  opened,  until  the  water 
has  descended  nearly  to  the 
bottom  mark,  and  a  correspond- 
ing quantity  of  air  has  entered 
into  the  burette.  After  waiting 
again  for  two  minutes,  the 
second  reading  is  made  and  the 
volume  of  the  gaseous  mixture 
thus  ascertained.  Since  2  vols, 
hydrogen  require  5  vols.  air,  100 
c.c.of  the  mixture  should  not  con- 


tain more  than 


100X2 


=  28-57 


c.c.  of  hydrogen ;  but  of  course 
this  utmost  limit  is  never  to  be 
FIG.  76.  attempted,   and   only  about  25 

c.c.  of  combustible  gas  must  be 
employed  if  this  gas  is  hydrogen. 

Much  less  combustible  gas  must  be  employed  in  the  case  of 
methane,  for  2  vols.  of  this  require  20  vols.  air  for  combustion ; 
hence  100  c.c.  in  the  burette  ought  not  to  contain  more  than — 


100  x  2 

22 


=  9-09  c.c.  methane. 


If  the  gaseous  remainder,  left  after  absorbing  CO2,  O,  CO, 
and  the  heavy  hydrocarbons,  contains  too  much  nitrogen  to 
enable  it  to  explode  after  mixing  with  air,  a  sufficient  amount 
of  pure  hydrogen  must  be  added.  This  is  best  kept  in  stock  in  a 
Hempel's  simple  hydrogen  pipette.  This  pipette,  Fig.  76,  is  similar 


HEMPEL'S  HYDROGEN  PIPETTES  159 

to  the  absorption  pipette  for  solid  reagents,  shown  in  Fig.  51, 
p.  85,  but  into  the  bottom  of  bulb  a  a  perforated  zinc  cylinder 
c  is  introduced  by  means  of  a  central  glass  rod  passing  through 
the  bottom  cork.  Bulb  b  contains  dilute  sulphuric  acid.  After 
all  air  has  been  expelled  from  the  apparatus,  the  side  capillary 
is  opened,  whereupon  hydrogen  issues  from  it  and  is  carried 
over  into  the  gas-burette  A,  Fig.  75,  in  the  well-known  way. 
If  the  capillary  is  closed  again,  the  hydrogen  expended  is 
renewed  by  the  contact  of  the  zinc  with  the  sulphuric  acid,  and 
it  forces  the  acid  out  of  a  into  bulb  b. 


FIG.  77. 

Fig.  77  shows  Hempel's  composite  hydrogen  pipette.  The 
lower  of  the  two  superposed  bulbs  a  and  a±  is  rilled  with  cuttings 
of  pure  zinc,  mixed  with  a  little  platinum  foil,  the  bottom  neck 
c  being  closed  by  a  rubber-covered  glass  rod.  Bulb  b  contains 
dilute  sulphuric  acid  (i  :  10),  introduced  through  the  lateral 
capillary  tube  by  means  of  a  long  funnel  tube,  during  which 
process  bulbs  b  and  c  are  getting  filled  with  hydrogen.  At  last 
a  little  mercury  is  poured  into  d,  but  for  ordinary  purposes  this 
can  be  replaced  by  water. 

The  gas  given  off  by  these  pipettes  is  never  absolutely  pure 
hydrogen,  but  contains  a  small  amount  of  air,  which,  however, 
does  not  affect  its  use  for  the  afore-mentioned  purpose. 

When  the  mixture  of  the  combustible  gas  with  air,  and  in 
case  of  need  also  with  a  measured  quantity  of  hydrogen  has 
been  made,  the  explosion  can  be  effected.  The  explosion 


160  TECHNICAL  GAS-ANALYSIS 

pipette  C,  Fig.  75,  p.  157,  is  placed  on  a  stand  D,  bulb  a  is 
filled  with  mercury  by  raising  b,  and  tap  h  is  closed.  The 
capillary  of  the  pipette  is  connected  by  means  of  the  capillary 
E  with  the  gas-burette  A,  tap  h  is  opened,  and  by  lifting  tube 
B,  the  pinchcocks  being  opened,  the  gaseous  mixture  is  trans- 
ferred from  A  into  the  explosion  bulb  a,  whereupon  the  taps 
are  again  closed.  Before  closing  tap  h,  it  is  best  to  lower  bulb 
b  and  thus  to  produce  a  partial  vacuum  in  a ;  but  if  the  volume 
of  gas  in  a  is  not  large,  and  it  is  not  highly  explosive,  tap  h 
may  even  be  left  open.  Now  the  battery  T  is  put  in  motion, 
the  current  is  closed,  and  the  explosion  at  once  takes  place  with 
a  flash,  the  mercury  being  agitated  and  covered  with  a  film. 
The  gas  is  then  retransferred  from  bulb  a  into  the  burette  A, 
and  after  the  water  in  the  latter  has  run  down  from  the  sides, 
the  contraction  is  measured. 

In  order  to  learn  the  manipulation  of  the  method,  we 
transfer  20  to  25  c.c.  hydrogen  from  the  hydrogen  pipette  into 
A,  make  the  reading,  admit  air  nearly  up  to  100  c.c.,  read  off 
the  volume  again,  transfer  the  mixture  into  the  explosion 
pipette  a,  close  the  current,  retransfer  the  gas  into  burette  A, 
and  read  off  the  contraction.  Example : 

Hydrogen  employed     .  .        .  .'  20-4  c.c. 

Hydrogen  +  air .  .  .  96-2  „ 

Hence  air  alone            .  .  75-8  „ 

Containing  oxygen        .  .  .  15-2  „ 

Oxygen  required  by  theory  . .  .  10-2  „ 

Excess  of  oxygen           .  .  .5-0  „ 

Volume  of  gas  after  explosion .  .  65-9  „ 

Contraction  (96-2  -  65-9)  ^  .  30-3  „ 


Found : — 


X  2  ,      j 

-   =  20-20  c.c.  hydrogen. 


We  pass  over  to  the  estimation  of  hydrogen  in  the  presence  of 
other  gases •,  but  in  the  absence  of  methane,  e.g.,  in  non-carburetted 
water-gas. — Carbon  dioxide  and  monoxide  are  successively 
removed  and  estimated  (pp.  1 17  and  126),  a  measured  portion  of 
the  gaseous  remainder  is  mixed  with  at  least  two  and  a  half  times 
its  volume  of  air,  the  mixture  after  measuring  its  volume  is 
introduced  into  the  explosion  pipette,  and  the  experiment 
finished  as  above. 


HEMPEL'S  HYDROGEN  PIPETTE  161 

Example : — 

Volume  of  water-gas  employed    .            .  99-80.0. 

After  treatment  by  potash             .            .  95-7  „ 

Contraction  .  .  x  .  .  4-1  „  =  4-12  per  cent.  CO2 
After  two  treatments  by  ammoniacal 

cuprous  chloride,  volume   .            .  56-0  „ 

Contraction  (95-7  -  56-0)         .            .  39.7  „    =  39.78        „         CO 
Gaseous  remainder  employed  for  com- 
bustion  (corresponding   to  43-13 

c.c.  of  the  original  gas)      .            .  24-2  „ 

After  addition  of  air          ,.-.      •'„•    •        •  98-3  „ 

Hence  air  admitted    .            .           . ,  74-1  „ 

Oxygen  contained  in  this  air             .  14-8  „ 

Nitrogen          .         /.^          .            .  59-3  „ 

Volume  of  gas  after  explosion      .            .  65-9  „ 

Contraction  (98-3-65-9)         .            .  32-4  „ 

Corresponding  to  hydrogen  in  the  gas  21-6  „    =  50-08        „         H 

„            oxygen  (from  the  air)  10-8  „ 

The  nitrogen  contained  in  the  original  gas  is  equal  to  the 
difference  between  the  volume  of  the  gas  not  absorbed  by 
potash  and  cuprous  chloride,  and  the  volume  of  hydrogen  found 
by  combustion : — 

Non-absorbed  gas  (=43-13  c.c.  of  the  original  gas)     24-2  c.c. 

Hydrogen  contained  therein  .  .  .     21-6   „ 

Remainder  (consisting  of  nitrogen)  .  .       2-6   „  =  6-02  per  cent. 

Final  result : — 

Carbon  dioxide  .  .  4-12  per  cent,  by  volume 

Carbon  monoxide  .  .  39-78         „  „ 

Hydrogen       .  .  .  50-08          „  „ 

Nitrogen         .  .  .  6-02          „  „ 

100-00 

Estimation  of  Methane  in  the  Absence  of  Hydrogen,  e.g.,  in 
Fire-damp. — To  such  a  mixture  of  methane  and  air  a  measured 
volume  of  pure  hydrogen  is  added  from  a  hydrogen  pipette.  If 
there  is  too  little  oxygen  present  more  air  (measured)  is  added, 
the  whole  is  transferred  into  the  explosion  pipette,  and  the 
current  closed.  After  this  the  gas  is  carried  back  into  the  gas- 
burette,  measured,  and  the  carbon  dioxide  formed  (whose 
volume  is  equal  to  that  of  the  original  methane)  is  estimated  by 
absorption  in  caustic  potash.  This  proceeding  is  safer  than 
calculating  the  methane  from  the  contraction  after  explosion, 
since  the  hydrogen  from  the  pipette  is  never  pure, 

L 


162  TECHNICAL  GAS- ANALYSIS 

Example : — 

Gas  employed          ".            ..      •    .  85-1  c.c. 

Gas  +  hydrogen        •  .            .  .  95-4  „ 

Hydrogen  alone         .            .  .  10-3  „ 

Volume  of  gas  after  explosion  .  70-5  „ 

After  absorption  by  potash  .  .  65-7  „ 

Contraction  (  =  CO2)  .            .  .  4-8  „ 

Equal  to  methane      .            .  4-8  „     =  5-63  per  cent. 

Estimation  of  Hydrogen  and  Methane  occurring  together,  e.g., 
in  Coal-gas,  Producer-gas,  Coke-oven  Gas,  Coal-pit  Gases,  etc. — The 
absorbable  gases  (CO2, 0,  CO,  C2H4,  etc.)  are  successively  removed 
and  estimated,  as  shown  in  previous  chapters.  Of  the  gaseous 
remainder,  from  8  to  1 5  c.c.  (according  to  whether  there  is  more 
methane  or  more  hydrogen  present)  is  transferred  into  a 
Hempel's  burette  and  measured,  air  is  added  nearly  up  to 
100  c.c.,  the  volume  measured  again,  the  mixture  transferred 
into  the  explosion  pipette,  and  the  contraction  by  explosion 
ascertained.  Now  the  volume  of  CO2  formed  is  found  by 
treating  the  gas  in  the  caustic  potash  pipette ;  this  volume  is 
equal  to  that  of  the  methane  originally  present,  which  on 
combustion  causes  a  contraction  of  twice  its  volume  (owing  to 
the  condensation  of  2H2O  formed).  By  deducting  this  from 
the  total  contraction  caused  by  the  explosion,  we  find  the 
contraction  caused  by  the  combustion  of  the  hydrogen,  two- 
thirds  of  which  is  equal  to  the  volume  of  the  hydrogen. 

We  shall  revert  to  this  subject  later  on  when  treating 
specially  of  methane. 

A  check  test  should  be  made  to  see  whether  sufficient  air 
had  been  employed  for  combustion,  by  transferring  the  last 
remainder  of  gas  to  a  phosphorus  or  pyrogallol  pipette,  which 
will  show  whether  there  is  still  oxygen  in  excess. 

We  give  an  example  of  the  analysis  of  coal-gas : — 

Gas  employed             .                         .  .  .  .            .     99-7  c.c. 

After    treatment    by    potash           •  95-9  c.c. 

Contraction          .            .            .  3-8  „  =     3-81  per  cent,  carbon 

After  treatment  by  fuming  sulphuric  dioxide 
acid    and     removal     of    the 

vapours  by  potash       .            .-  91-2  „ 

Contraction          .          •  \-        •  ;  47  »  =    47 1          »         heavy 

After  treatment  by  pyrogallol-potash  90-6  „  hydrocarbons 

Contraction         .            .            .  0-6  „  =    0-60  per  cent,  oxygen 


PFEIFFER'S  EXPLOSION  PIPETTE 


163 


After     treatment     by     ammoniacal 

cuprous  chloride 
Contraction 
Non-absorbed  gas 
Of  this  employed  for  the  combustion 

( =  1 5-07  of  original  gas) 
Ga.sfl/us  air  . 
Hence  air  alone 
Containing  oxygen 

,,  nitrogen  . 

Volume  after  explosion 
Total  contraction  (99-0-79-0) 
After  treatment  with  potash 
Contraction  (  =  CO2)  . 

=  Methane  in  15-07  original  gas 
Contraction  caused  by  combustion 

of  methane  (4-6  x  2)     . 

Contraction  caused  by  combustion 

of  hydrogen  (20-0-9-2) 

2X  10-8 


8o-7  c.c. 

9-9  „    =    9-93  per  cent,  carbon 

80-7  „  monoxide 

12-2  „ 

99-o  „ 

86-8  „ 

17-4  „ 

69-4  » 

79-o  „ 

20-0  „ 

74-4  „ 

4-6  „ 
4-6 

9-2 


=  30-52  per  cent,  methane 


10-8    „ 
7-2    „     =  47-78 


hydrogen 


Estimation  of  nitrogen  : — 

Unabsorbed  gas  employed  (=15-07 
per  cent,  of  the  original  gas, 
as  before)  .  . 

Containing  methane  .  4-6  c.c. 

„  hydrogen  7-2  c.c. 

Leaving  a  remainder  of         .  . 

Summary : — 

Carbon  dioxide 
Heavy  hydrocarbons 
Oxygen  t 

Carbon  monoxide 
Methane         v^ 
Hydrogen       .  . 

Nitrogen 


12-2  C.C. 


0-4   „     =  2-65  per  cent,  nitrogen 


3-81  per  cent,  by  volume 

471         » 
0-60         „ 

9'93         » 
30-52 
4778 

2-65 


100-00 


PfeiffeSs  explosion-pipette,  Fig.  78,  admits  of  working  with 
water  in  lieu  of  mercury,  by  avoiding  the  absorption  of  CO2  by 
the  water  in  the  following  manner : — Before  the  explosion,  the 
water  is  drawn  from  the  explosion  bulb  A  into  bulb  B,  for 
which  purpose  the  taps  a  and  b  are  provided.  The  peculiar 


164 


TECHNICAL  GAS-ANALYSIS 


FIG.  78. 


arrangement  of  the  platinum  points  in  A  avoids  the  formation 
of  drops  between  them  (Chem.  Zeit.,  1904,  p.  686.  This 
pipette  is  supplied  by  H.  Horold,  glass-blower,  of  Magdeburg). 
In  order  to  avoid  the  squirting  on  the  return 
of  the  confining  water  into  A,  after  opening 
tap  b,  a  drop  of  mercury  is  put  into  the 
connecting  (J-tube. 

2.  Combustion  by  Means  of  Heated  Plati- 
num or  Palladium. — Several  metals  of  the 
platinum  group,  viz.,  platinum,  iridium,  and 
especially  palladium,  have  the  property  of 
causing  the  combustion  of  various  gases  by 
oxygen  at  temperatures  below  the  point  of 
inflammation,  and  that  all  the  better,  the 
finer  the  state  of  division  and  consequently 
the  greater  the  surface  offered  by  these 
metals  to  the  gases.  Especially  easy  and  complete  is  the 
combustion  of  hydrogen,  if  mixed  with  a  sufficient  quantity  of 
air  and  carried  over  gently  heated,  finely  divided  palladium. 
Under  the  same  conditions  carbon  monoxide,  ethylene,  and 
benzene  are  burned  with  a  little  more  difficulty,  but  also 
completely.  Methane,  however,  whose  temperature  of  inflam- 
mation is  very  high  (about  790°)  remains  unchanged  at 
moderately  low  temperatures.  From  this  follows  the  possi- 
bility of  estimating  the  more  easily  burning  gases,  especially 
hydrogen,  in  the  presence  of  methane  by  means  of  fractional 
combustion. 

The  first  to  apply  fractional  combustion  for  this  purpose  was 
W.  Henry  (Annals  of  Philosophy,  xxv.  p.  428),  who  employed 
platinum  sponge  heated  to  177°,  but  his  proposal  did  not  lead 
to  practical  results  in  gas-analysis.  This  only  ensued  on  the 
labours  of  Clemens  Winkler,  who  published  his  method,  founded 
on  the  application  of  finely  divided  palladium  in  the  shape  of 
"  palladium  asbestos,"  in  1877,  in  his  Anleitung zur  Untersuchung 
der  Industrie-Case  "  ii.  pp.  257  et  seq.  Later  on  Bunte  (Ber.> 
1878,  p.  1123)  proposed  palladium  wire,  Hempel  (Ber.,  1879, 
p.  1006)  superficially  oxidised  palladium  sponge  at  a  temperature 
of  100°.  Winkler's  method  has,  however,  remained  victorious, 
and  his  palladium  asbestos  is  employed  in  most  of  the  modern 


PALLADIUM  ASBESTOS  165 

apparatus   for   technical  gas-analysis,  e.g.,  in  the  Orsat-Lunge 

(P.  70; 

Winkler's  combustion  apparatus  consists  of  a  short  glass 
capillary  tube,  bent  at  each  end  in  a  right  angle,  into  which  a 
fibre  of  asbestos,  impregnated  with  finely-divided  asbestos,  has 
been  loosely  introduced,  so  that  it  does  not  impede  the  passage 
of  the  gas.  This  palladium  asbestos  is  prepared  in  the  following 
way  : — Dissolve  I  g.  palladium  in  aqua  regia,  evaporate  the 
solution  on  a  water-bath  to  dryness,  whereby  any  adhering 
hydrogen  chloride  should  be  removed  as  completely  as  possible, 
and  dissolve  the  palladium  chloride  thus  produced  in  a  little 
water.  (Or  else  employ  a  solution  of  3  g.  sodium  palladium 
protochloride  in  a  small  quantity  of  water.)  Add  a  few  cubic 
centimetres  of  a  cold  saturated  solution  of  sodium  formate  and 
sufficient  sodium  carbonate  to  produce  a  strongly  alkaline 
reaction.  Now  introduce  I  g.  of  very  soft,  long-fibred  asbestos, 
which,  if  any  unnecessary  excess  of  water  has  been  avoided, 
absorbs  the  whole  liquid,  forming  a  thick  paste.  This  is  dried 
at  a  gentle  heat,  by  which  process  black,  finely  divided  palladium 
is  uniformly  precipitated  upon  the  asbestos  fibre.  In  order  to 
make  the  palladium  adhere  upon  the  asbestos,  the  product  thus 
prepared  is  heated  on  a  water-bath  till  completely  dry,  put  into 
a  glass  funnel  and  freed  from  all  adhering  salts  by  thorough 
washing,  no  palladium  being  removed.  After  drying,  the 
substance  shows  a  dark  grey  colour,  with  a  slight  tendency  to 
stain  the  fingers  on  being  touched,  and  contains  about  50  per 
cent,  palladium.  It  possesses  a  very  high  degree  of  chemical 
activity  ;  in  the  perfectly  dry  state  it  causes  the  combination  of 
hydrogen  and  oxygen  even  at  the  ordinary  temperature,  but  to 
make  sure  of  attaining  this  it  is  always  employed  in  the  heated 
state.  (The  same  process  is  employed  for  preparing  platinum 
asbestos,  required  for  other  purposes,  but  this  is  generally  made 
with  only  10  to  25  per  cent,  platinum.) 

In  the  place  of  the  palladium  asbestos,  which  easily  shifts 
its  place  in  the  capillary  tube,  Leutold  (as  communicated  to 
Treadwell,  Lehrbuch,  etc.,  vol.  ii.  p.  545)  applies  a  spiral  of 
palladium  wire. 

The  tubes  for  receiving  the  palladium  asbestos  are  capillary 
glass  tubes,  about  I  mm.  bore  and  6  mm.  outside  diameter, 
cut  in  pieces  i6or  18  cm.  long.  The  asbestos  fibre  is  introduced 


166  TECHNICAL  GAS-ANALYSIS 

into  them  in  the  following  way : — A  few  loose  fibres  of  the 
palladium  asbestos  are  laid  alongside  each  other  on  smooth 
filtering  paper  up  to  a  length  of  4  cm.  They  are  moistened 
with  a  few  drops  of  water,  and,  by  passing  the  finger  over  them, 
are  twisted  into  a  fine,  straight  thread,  which  in  the  moist  state 
has  the  thickness  of  a  stout  sewing  cotton.  This  thread  is 
grasped  at  one  end  with  the  nippers,  and,  without  bending  or 
nicking,  is  slid  from  above  into  the  (vertically  held)  capillary 
tube.  This  tube  is  then  filled  with  water,  and  by  jerking  or 
drawing  this  off  at  the  ends,  the  asbestos  thread  is  brought  into 
the  centre  of  the  tube,  which  is  now  dried  in  a  warm  place. 
When  dry,  the  ends  are  bent  off  at  a  right  angle  for  a  length  of 
35  or  40  mm.,  and  the  edges  rounded  off  with  the  lamp.  (The 
dealers  in  chemical  apparatus  supply  capillaries  already  charged 
with  palladium  asbestos.) 

Manipulation. — The  volume  of  the  combustible  gas  contained 
in  the  gas-burette  A,  Fig.  79,  is  read  off;  it  should  in  no  case 
exceed  25  c.c.  The  levelling  tube  is  placed  on  the  floor  of  the 
room,  and  by  opening  the  pinchcock,  enough  air  is  admitted  to 
bring  up  the  total  volume  of  the  gas  to  nearly,  but  not  quite, 
100  c.c.  When  all  the  water  has  run  together,  the  volume  of 
the  gas  is  read  off.  The  capillary  tube  E  is  now  placed 
between  the  burette  A  and  the  pipette  C,  and  heated  for  one  or 
two  minutes  by  means  of  the  small  gas-jet  F  (or  a  spirit-lamp) ; 
but  not  too  much,  certainly  not  to  a  visible  red  heat,  or  until 
the  glass  softens.  The  combustion  can  now  begin  by  elevating 
the  levelling  tube,  opening  the  pinchcocks,  and  passing  the 
gaseous  mixture  in  a  slow  stream  through  the  heated  palladium 
asbestos  into  the  pipette  C.  That  end  of  the  asbestos  thread 
which  is  opposite  to  the  entrance  of  the  gaseous  current  begins 
to  glow  visibly,  and  this  glowing  frequently  reappears  when 
conveying  the  gas  back  into  the  burette.  All  the  time  the 
flame  is  left  burning  under  the  capillary  tube,  taking  care  not 
to  pass  the  gas  through  too  quickly,  and  that  no  drops  of  water 
should  get  into  the  capillary,  which  would  then  be  sure  to  crack. 
In  the  case  of  easily  burning  gases,  the  combustion  is  generally 
finished  by  passing  the  gas  twice  forward  and  backward ;  but  in 
any  case  we  have  to  make  sure  by  another  passage  that  no 
further  contraction  takes  place.  The  remaining  gas  is 
measured,  and  the  contraction  produced  is  thus  ascertained. 


MANIPULATION 


167 


From  this  the  quantity  of  the  gas  burned  is  calculated,  either 
directly,  or  after  removing  any  carbon  dioxide  formed  by  the 
combustion,  and  ascertaining  the  decrease  of  volume  thus 
produced. 

By  this  method  hydrogen  is  burned  very  easily  and  quickly ; 
carbon  monoxide  a  little  less  easily,  but  still  quite  conveniently  ; 
ethylene,  acetylene,  and  benzene  more  slowly,  and  only  by  heating 
more  strongly.  Methane  is  not  burned  at  all ;  even  when  a 
considerable  excess  of  easily  combustible  gases  is  present,  no 


FIG.  79. 

methane,  or  at  most  only  extremely  slight  traces  of  it  is 
burned  with  them,  according  to  Winkler.  But  if  the  tempera- 
ture rises  too  much,  a  little  methane  is  burned  as  well.  In 
fact  Tread  well  (Lehrb.  d.  quant.  Analyse,  4th  ed.,  p.  575)  finds 
that  the  results  are  generally  too  high  by  0-5  to  I  per  cent. 
On  the  strength  of  only  two  experiments  Charitschkow  (Chem. 
Centr.  1903,  i.  p.  295)  even  asserted  that  Winkler's  method  does 
not  admit  of  anything  like  the  exact  separation  of  hydrogen 
and  methane  ;  but  Brunck  (Z.  angew.  Chem.,  1903,  p.  695)  proved 
this  assertion  to  be  entirely  wrong,  and  found  Winkler's  method 
to  be  quite  correct,  if  carried  out  as  prescribed  by  its  author 


168  TECHNICAL  GAS-ANALYSIS 

(and  supra}.  In  no  case  must  oxygen  be  employed  for  the 
combustion  in  the  place  of  air,  because  in  this  case  a  portion 
of  the  methane  would  be  burned  as  well  (Brandt,  Z.  angew. 
Chem.,  1903,  p.  695). 

A  very  complete  investigation  of  the  combustion  by  means 
of  the  catalytic  action  of  hot  palladium  has  been  made  in  Bunte's 
laboratory  by  Richard t  (/.  Gasbeleucht.,  1904,  pp.  566  et  seq.  and 
590  et  seq.\  who  in  the  beginning  of  his  paper  enumerates  the  very 
extensive  literature  on  this  subject.  He  employed,  as  Bunte  had 
previously  done,  palladium  in  the  state  of  a  solid  wire  in  lieu  of 
palladium  asbestos,  because,  in  consequence  of  the  good  heat- 
conducting  capacity  of  such  wire,  it  is  easier  to  avoid  any 
considerable  inequalities  of  temperature.  He  found,  as  Haber 
had  previously  done,  that  at  temperatures  below  450°  methane 
is  not  burned  by  the  catalytic  action  of  palladium  wire.  Above 
450°,  and  still  below  a  visible  red  heat,  in  all  cases  notable 
quantities  of  methane  are  burned,  if  the  contact  with  the 
catalyser  lasts  sufficiently  long.  During  a  short  contact  a 
current  of  methane  and  air  passes  over  the  palladium  wire 
without  noticeable  combustion  even  at  600°  to  650°,  whilst  any 
hydrogen  present  is  completely  burned.  The  combustion  of 
methane  is  not  influenced  by  that  of  hydrogen,  even  in  a  slow 
passage  of  the  gases.  In  order  to  carry  out  an  analysis,  a 
measured  quantity  of  the  combustible  gases  is  mixed  with  air 
and  is  passed  through  a  tube,  heated  by  a  small  Bunsen  burner 
in  the  midst  of  which  tube  a  palladium  wire,  plied  several  times 
upon  itself,  is  placed.  The  heat  must  not  go  up  to  the  point 
where  the  palladium  wire  shows  a  red  glowing,  because  in  this 
case  notable  quantities  of  methane  are  burned.  Bunte  has 
found  that  the  proper  temperature  is  reached  when  the  Bunsen 
flame  begins  to  exhibit  the  coloration  due  to  the  potassium  or 
sodium  contained  in  the  glass  of  the  capillary,  which  in  the 
case  of  pretty  high-fusible  glass  takes  place  at  a  temperature 
of  550°  to  600°.  At  this  temperature  no  methane  but  all  the 
hydrogen  is  burned.  To  make  sure  of  the  completeness  of 
the  combustion,  the  gas  may  be  passed  a  second  time  over  the 
palladium,  in  which  operation  the  temperature  may  be  kept 
rather  higher,  since  now,  after  the  hydrogen  is  removed,  there 
is  no  danger  of  any  methane  getting  burned.  Ethane  behaves 
similarly  to  methane,  and  these  two  hydrocarbons  cannot  be 


FRACTIONAL  COMBUSTION  169 

separated  by  fractional  combustion.  Ethylene  begins  to  burn 
already  at  300°,  but  it  cannot  be  estimated  by  fractional 
combustion  in  a  mixture  with  ethane  or  methane,  because,  in 
order  to  burn  it  quantitatively,  a  temperature  must  be  employed 
at  which  methane  is  already  beginning  to  burn.  The  estima- 
tion of  ethylene  is  most  simply  carried  out  by  treatment  of 
the  gas  with  bromine  water  (cf.  p.  119). 

Philip  and  Steele  (B.  P.  27281  of  1911)  describe  the  con- 
struction and  operation  of  a  draught-proof  catalytic  combustible 
gas-detector,  comprising  a  wire  adapted  to  be  heated  by  the 
catalytic  combustion  of  the  gas  to  be  tested,  and  means  for 
indicating  the  resulting  change  in  the  resistance  of  the  wire. 

L.  A.  Levy  (/.  Gas  Lighting,  cxxii.  p.  524)  employs  an 
electrically  heated  platinum  spiral,  followed  by  a  quartz 
capillary. 

The  fractional  combustion  of  mixtures  of  hydrogen  and 
methane  with  air  by  the  action  of  heated  palladium  has  been 
already  described  supra,  pp.  71  et  seq.,  as  carried  out  by  means 
of  the  Orsat- Lunge  apparatus. 

Bunte  gives  the  following  prescriptions  for  carrying  out  the 
fractional  combustion  of  such  gaseous  mixtures  when  employing 
his  burette,  described  supra,  pp.  58  et  seq.  Besides  this  burette 
A,  a  second  burette  B  is  required.  In  the  burette  A  22  to 
25  c.c.  of  the  non-absorbable  gases  are  measured  off  and  mixed 
with  the  air  required  for  combustion.  For  this  purpose  first 
the  lower  tap  is  opened,  then  the  upper  tap  in  such  manner  that 
it  is  in  communication  with  the  outer  air,  which  now  enters 
as  the  water  is  running  out.  When  the  water  level  has  gone 
down  to  about  5  c.c.  below  O,  first  the  upper  tap  is  quickly 
closed,  then  the  lower  tap,  the  gases  are  mixed  by  shaking  the 
burette,  the  pressure  is  made  equal  to  that  of  the  atmosphere, 
plus  the  column  of  water  in  the  funnel,  and  the  reading  is 
taken.  Now  burette  B  is  filled  with  water  up  to  the  capillary 
tube,  and  both  three-way  taps  are  connected  with  the  inter- 
position of  a  palladium  tube  C.  This  tube  is  made  of  glass 
of  high-fusing  point,  10  cm.  long,  5  mm.  wide  outside  diameter, 
and  3  mm.  wide.  The  palladium  wire  is  100  mm.  long,  0-5  mm. 
thick;  it  is  plied  four  times  upon  itself  and  introduced  into  the 
tube  up  to  the  centre.  This  place  is  now  narrowed  by  heating 
the  tube  up  to  getting  soft,  so  that  the  wire  is  held  fast  here ; 


170  TECHNICAL  GAS- ANALYSIS 

the  remaining  portion  of  the  tube  is  loosely  filled  with  long- 
fibred  asbestos  (see  Fig.  80).  Tube  Cx  is  connected  with  the 
burettes  A  and  B  by  short,  thick-walled  rubber  tubes. 

Now  both  three-way  taps  are  turned  so  that  none  of  their 
bores  are  open  ;  the  funnel  of  burette  A  is  filled  with  water ; 
by  briefly  opening  its  lower  tap,  the  pressure  in  it  is  reduced ; 
both  three-way  taps  are  at  the  same  time  quickly  turned  in 
such  manner  that  the  palladium  pipe  communicates  with  the 
interior  space  of  both  burettes,  and  C  is  heated,  whereby  the 
air  is  expanded  and  forces  the  water  from  the  top  capillaries 

back  into  the  burettes.  The 

rubber  tube  of  the  pressure 

'    bottle  is  connected  with  the 

FlG  8o  bottom  tap  of  A,  this  tap  is 

opened,  tube  C  is  heated  at 

the  contracted  place  until  the  small  flame  turns  yellow,  and 
the  bottom  tap  of  B  is  opened  so  far  that  the  gas  travels  in 
a  moderately  fast  stream  from  A  through  C  into  B.  The 
water  should  flow  out  of  B  in  a  jet,  not  in  drops,  and  the 
palladium  wire  at  the  entrance  end  of  the  gas  is  not  to  turn 
red-hot  (because  in  that  case  a  little  methane  would  be  burned 
as  well).  At  the  moment  when  the  water  in  burette  A  has 
got  up  to  the  top,  first  its  bottom  tap,  then  that  of  B  is  closed, 
and  the  gas  is  in  the  same  way  as  before  carried  back  from 
B  into  A ;  here,  after  cooling,  the  pressure  is  made  normal, 
the  reading  is  taken,  and  thereby  the  contraction  is  ascertained. 

Example : — 

Volume  of  the  gaseous  remainder  from  100  c.c.  coal-gas,  after 
absorbing  CO2,  heavy  hydrocarbons,  oxygen,  and  carbon 

monoxide          .  ...  .  .  .  85-0  c.c. 

Employed  of  this  for  combustion  .        •    .  .  »  .  22-2   „ 

Volume  after  dilution  with  air        .  .  .  .  .  105-3   „ 

„  combustion   .  .    .         .  .  .  .  19-0  „ 

Contraction  calculated  on  the  original  volume  I9'ox    5'°  ~2.g 

22-2 

Corresponding  to  2X  ^2'    hydrogen          ....        48-5   „ 

As  a  control,  the  oxygen  left  after  the  explosion  is  deter- 
mined ;  its  volume  should  be  equal  to  one-third  of  the 
contraction. 


BUNTE'S  EXPLOSION  BURETTE  171 

Methane  is  estimated  (together  with  hydrogen)  in  the  same 
gaseous  remainder  from  the  absorbing  operations  in  Bunte's 
explosion  burette,  i.e.,  a  Bunte  burette  with  platinum  points 
fused  in  near  the  top.  In  this  12  to  15  c.c.  of  the  gas  is 
measured  off,  an  excess  of  air  is  drawn  in,  mixed  by  shaking, 
measured,  the  water  level  is  lowered,  the  explosion  is  effected 
by  an  electric  spark,  the  contraction  is  read  off,  I  or  2  c.c.  of 
caustic  potash  solution  is  run  down  along  the  glass  walls,  water 
is  slowly  allowed  to  get  in,  the  pressure  is  again  made  normal, 
and  the  "  total  contraction  "  (due  to  the  formation  of  CO2  and 
H2O)  is  ascertained.  Deducting  therefrom  the  amount  due 
to  the  combustion  of  hydrogen  (as  ascertained  supra),  one- 
third  of  the  remaining  contraction  indicates  the  volume  of  the 
methane,  since  for  each  volume  of  this  2  vols.  of  oxygen  have 
vanished. 

Example : — 

Gaseous   remainder   employed    (from   85    c.c.,  left  after 

absorbing  CO2,  CmHn,  O2,  and  CO2)     .  .  .         12-7  c.c. 

Volume  after  adding  air        .            .  .  .  104-1    „ 

Hence  air  added         .            .                        .  .  .        91-4  „ 

Volume  after  explosion          .            -..            .  .  .        78-9   „ 

Hence  total  contraction                      .            .  .  .        25-2   ,, 

The  same  calculated  on  the  whole  gas  — —    .  .       168-8  „ 

Deducting  therefrom  the  72-2  due  to  the  combustion  of 

hydrogen,  as  found  supra,  remain          ,.  .  .        96-0  „ 

One-third  of  which  indicates  the  methane  .  .  .        32-0  per  cent. 

In  cases  where  the  gas  remaining  after  the  absorption  of 
CO2,  illuminants  O  and  CO,  is  too  poor  to  be  exploded  without 
the  addition  of  hydrogen,  Vail  (/.  Ind.  and  Eng.  Chem.,  1913, 
p.  756)  recommends  enriching  it  by  the  formation  of  hydrogen 
and  oxygen  by  means  of  an  electric  arch,  after  addition  of 
water  for  that  purpose. 

Felser  (Ger.  P.  266046)  describes  an  apparatus  for  ascer- 
taining the  incomplete  combustion  of  fire-gases  by  effecting 
the  complete  combustion  by  means  of  a  catalytical  substance 
(platinum  coated  with  palladium),  interposed  between  two 
thermo-elements,  so  that  the  rise  of  temperature  after  the 
complete  combustion  can  be  measured  and  catalysed  for 
estimating  the  combustible  gases  originally  present. 


172  TECHNICAL  GAS-ANALYSIS 

3.  Combustion  of  Methane  by  Heated  Platinum.  —  This  method 
has  been  already  described  in  connection  with  Hempel's  (supra 
p.  92)  and  Drehschmidt's  apparatus  (supra  p.  103).     We  shall 
later  on  describe  its  application  to  the  testing  of  the  air  of 
coal-pits  by  Coquillion's  Grisoumeter  and  other  apparatus. 

4.  Combustion  of  Nitrogen  by  Oxygen  through  the  Action  of 
Electric    Sparks.  —  This   process   has   been    first   employed    by 
Lord  Rayleigh.     Henrich  and  Eichhorn  (Z.  angew.  Chem.,  1912, 
p.  468)  describe  an  arrangement  of  apparatus,  by  which  free 
nitrogen  can  be  comparatively  quickly  removed  quantitatively 
from  gaseous  mixtures  through  the  action  of  electric  sparks  in 
the  presence  of  oxygen  and  of  caustic   soda   solution  which 
absorbs  the  nitrogen  oxides  formed. 

5.  Combustion     by   Cupric   Oxide.  —  This    method,   which   is 
due  to  Jaeger  (/.  Gasbeleucht.,  1898,  p.  764),  depends  upon  the 
fractional  combustion  of  the  mixture  of  gases  by  cupric  oxide 


FIG.  81. 

at  varying  temperatures.  As  the  oxygen  required  for  the 
combustion  is  not  added  in  the  gaseous  form,  but  is  furnished 
by  CuO,  the  relations  of  the  volume  changes  are  very  simple. 
The  hydrogen  disappears  completely  on  burning  and  its 
volume  is  equal  to  the  contraction  ;  methane  forms  its  own 
volume  of  carbon  dioxide,  which  is  easily  measured  by  absorp- 
tion. The  cupric  oxide  is  placed  in  a  small  tube  of  the  form 
shown  in  Fig.  81,  which  is  made  of  hard  Jena  glass,1  with 
a  capillary  on  one  side  and  a  somewhat  wider  tube  on  the 
other.  To  fill  the  tube,  large  grained  cupric  oxide  is  intro- 
duced, so  that  it  lies  at  the  beginning  of  the  capillary,  and 
a  plug  of  asbestos  fibre  placed  against  it  ;  the  wide  part  of 
the  tube  is  then  filled  with  freshly  ignited,  powdered  cupric 

1  Since  glass  are  easily  bent  by  heating  and  crack  when  a  drop  of 
water  gets  in,  Knorre  (Chem.  Zeit.^  1909,  No.  79)  employs  tubes  of  quartz- 
glass,  10  cm',  long,  5  mm.  wide,  and  0-5  to  075  thickness  of  the  walls 
(supplied  by  Dr  Siebert  &  Kiihn,  of  Kassel). 


COMBUSTION  BY  CUPRIC  OXIDE  173 

oxide,  which  is  kept  in  position  by  a  second  plug  of  asbestos. 
The  tube  is  connected  by  rubber  tubing  on  one  side  with  the 
measuring  burette,  and  on  the  other  side  with  the  absorption 
pipette,  charged  with  potassium  hydroxide  solution.  For  the 
combustion  of  the  hydrogen  the  tube  is  heated  to  250° ;  this 
temperature  is  controlled  by  means  of  a  thermometer,  the  bulb 
of  which  is  placed  close  against  the  tube.  After  oxidising  the 
hydrogen  and  reading  the  contraction,  the  thermometer  is 
removed  and  the  methane  then  oxidised  by  heating  the  cupric 
oxide  to  a  red  heat.  As  the  carbon  dioxide  formed  is  absorbed 
by  the  potassium  hydroxide  in  the  pipette,  the  reduction  of 
volume  indicates  the  volume  of  the  methane  directly. 

The  combustion  with  cupric  oxide  has  the  great  advantage 
over  other  methods  that  the  whole  of  the  gas  left  after 
absorption  can  be  taken  for  the  determination,  so  that  any 
errors  do  not  influence  the  final  result  to  the  same  extent  as 
when  only  a  fraction  of  the  residue  is  used.  There  is,  however, 
the  drawback  that  the  methane  is  not  easily  burnt  completely, 
and  that  the  temperature  of  combustion  is  so  high,  since  the 
tube  must  be  allowed  to  cool  down  before  reading  the  volume ; 
the  reduced  copper  must  also  be  oxidised  after  each  analysis. 

The  apparatus  employed  by  Jaeger  is  shown  in  Fig.  82. 
The  burette  is  a  modified  form  of  that  of  Bunte,  narrowed  at 
the  top  to  permit  of  more  accurate  readings,  and  provided  with 
a  lateral  exit-tube ;  it  is  enclosed  in  a  water-jacket.  The 
absorptions  are  carried  out  with  Hempel  pipettes  in  the  usual 
way.  For  the  fractional  combustion  of  the  hydrogen  and 
methane,  the  cupric  oxide  tube  is  connected  by  rubber  tubes  s 
with  the  burette,  and  by  s2  (both  of  them  bound  with  wire)  with 
a  Hempel  pipette  filled  with  potassium  hydroxide  solution. 
Below  the  combustion  tube  is  placed  the  Bunsen  burner  b, 
which  is  provided  with  a  special  regulating-tap  and  a  fan-shaped 
fitting  to  the  burner.  A  framework  of  sheet  iron  attached  to 
the  burner  carries  a  cover  in  which  a  short  thermometer, 
graduated  up  to  270°,  is  fixed  so  that  its  side  lies  close  to  the 
side  of  the  combustion  tube.  At  the  beginning  of  the  test  the 
solution  in  the  pipette  is  forced  up  to  the  mark  m  of  the 
capillary  by  blowing  through  the  tube  ss  while  the  upper 
burette  cock  is  in  the  position  I ;  this  stopcock  is  then  closed 
by  a  quarter  turn  (position  III),  and  the  tube  slowly  heated  to 


174 


TECHNICAL  GAS-ANALYSIS 


250°  and  kept  at  this  temperature  with  as  little  variation  as 
possible.  As  soon  as  this  temperature  has  been  reached,  the 
upper  stopcock  of  the  burette  is  opened  (position  II),  then  the 
lower  one  and  the  levelling  bottle  raised.  By  passing  the  gas 


FIG.  82. 


slowly  from  the  burette  to  the  pipette  and  back  again,  the 
hydrogen  is  completely  oxidised.  After  allowing  to  cool,  the 
water  in  the  pipette  is  again  brought  to  the  mark  m,  and  the 
residual  gas  measured. 


COMBUSTION  BY  CUPRIC  OXIDE  175 

A  correction  has  to  be  applied  for  the  oxygen  of  the  air 
initially  enclosed  in  the  combustion  tube,  which  participates  in 
the  oxidation  of  the  hydrogen.  This  is  made  once  for  all  by 
filling  the  burette  with  pure  hydrogen  and  determining  the 
value  of  the  correction  ;  it  amounts  to  about  0-5,  and  must  be 
subtracted  from  the  hydrogen  contraction  found  in  the 
subsequent  testings.  This  correction  must  also  be  made  in  the 
determination  of  the  nitrogen  at  the  end  of  the  analysis. 

For  the  subsequent  combustion  of  the  methane,  the  cover 
with  thermometer  over  the  combustion  tube  is  removed,  the 
tube  heated  with  a  more  powerful  flame  to  a  bright  red  heat, 
and  the  gas  repeatedly  carried  over  the  cupric  oxide,  till  no 
further  decrease  in  volume  takes  place.  The  carbon  dioxide 
formed  by  the  combustion  is  retained  in  the  alkali  pipette ;  the 
decrease  in  volume,  therefore,  corresponds  directly  (without 
correction)  to  the  methane  present.  The  residual  gas  must  be 
allowed  to  cool  completely  to  the  temperature  of  the  room 
before  taking  the  final  reading. 

The  incombustible  gas  residue,  increased  by  the  volume  of 
the  oxygen  previously  enclosed  in  the  cupric  oxide  tube  and 
afterwards  consumed  (correction  -  value),  gives  the  nitrogen 
content  of  the  air. 

For  the  determination  of  the  percentage  of  nitrogen  only  in 
a  sample  of  gas,  the  latter  is  introduced  into  the  burette,  the 
cupric  oxide  tube  at  once  heated  to  a  high  temperature,  and 
the  gas  passed  backwards  and  forwards  into  the  potash  pipette 
until  no  further  contraction  occurs.  The  whole  of  the  gaseous 
constituents,  other  than  nitrogen,  are  thus  completely  removed, 
and  the  residual  volume  of  gas,  read  after  complete  cooling, 
plus  the  previously  ascertained  correction  for  the  oxygen 
content  of  the  cupric  oxide  tube,  gives  directly  the  amount 
of  nitrogen  in  the  gas,  and  its  percentage  if  100  c.c.  have  been 
taken.  Where  many  such  tests  have  to  be  made,  it  is 
convenient  to  displace  the  air  in  the  cupric  oxide  tube  by 
nitrogen  previous  to  the  test,  in  which  case  no  correction 
is  necessary. 

After  each  test  the  cupric  oxide  tube  must  be  heated  in  a 
current  of  air  to  reoxidise  the  reduced  copper. 

The  results  of  this  method  are  satisfactory  as  regards 
accuracy.  The  combustion  of  the  methane  is,  however,  very 


176  TECHNICAL  GAS-ANALYSIS 

slow,  and  varies  greatly  according  to  the  physical  condition  of 
the  oxide  of  copper. 

Cupric  oxide  is  also  used  by  Winkler  in  his  apparatus  for 
the  estimation  of  methane  in  pit  air,  which  will  be  described 
later  on.  Other  apparatus  for  burning  gases  by  means  of 
cupric  oxide  have  been  described  by  Ubbelohde  and  de  Castro 
(/.  Gasbeleucht.,  1911,  p.  810);  Hohensee  (ibid.,  1911,  p.  814); 
Worrell  (Metallurg.  Chem.  Engin.,  1911,  p.  576  ;  Z.  angew.  Chem., 
1912,  p.  915);  the  "Metrogas"  apparatus  (/.  Gas  Lighting, 
191 1,  p.  819) ;  Dennis  (his  Gas  Analysis,  p.  201). 

GrebeFs  ucomburimeter "  (J.  Gas  Lighting.,  cxxi.  p.  738) 
measures  the  quantity  of  air  or  oxygen  required  for  burning 
the  gas,  by  means  of  a  special  instrument,  the  "  comburimeter," 
consisting  of  a  burner  with  chimney,  with  exactly  regulated 
supply  of  air  and  gas,  in  which  an  excess  of  oxygen  in  the 
flame  is  recognised  by  the  change  of  colour  of  a  drop  of 
melted  lead. 


IV.    GAS-ANALYSIS  BY  OPTICAL  AND  ACOUSTICAL 
METHODS. 

A  large  number  of  chemists  and  physicists,  beginning  from 
Dulong  in  I826,1  have  studied  the  optical  behaviour  of  gases, 
and  more  especially  their  refractometric  properties.  We  owe 
it,  however,  only  to  the  labours  of  Professor  Haber  and  his 
students,  that  these  properties  have  led  to  practical  results  for 
the  purpose  of  scientific  and  technical  gas-analysis. 

Haber's  gas-refractometer  (supplied  by  Carl  Zeiss,  of  Jena) 
is  constructed  on  the  principles  laid  down  by  Lord  Rayleigh 
(Proc.  Roy.  Soc.,  1896,  p.  203)  and  Ramsay  and  Travers  (ibid., 
1897,  p.  225),  but  many  difficulties  had  to  be  overcome  before 
an  instrument  fit  for  practical  use  had  been  worked  out.  This 
instrument  has  been  described  by  Haber  in  Z.  angew.  Chem.,  1906, 
p.  1418,  and  in  Z.  Elektrochem.,  1907,  p.  460.  A  long  paper  by 
Stuckert  (ibid.,  1910,  pp.  37  to  75)  describes  the  researches  made 
by  means  of  this  with  a  number  of  gases.  We  refrain,  however, 
from  going  into  this,  as  Haber  has  later  on,  in  conjunction  with 
Dr  Lowe,  of  the  firm  of  Carl  Zeiss,  worked  out  another 

1  The  literature  of  this  subject  is  enumerated  in  the  paper  of  Stuckert, 
mentioned  in  the  text. 


OPTICAL  METHODS  177 

instrument  which  is  much  more  easily  manipulated,  especially 
for  technical  purposes.  This  instrument,  called  interferometer, 
is  described  by  Haber  and  Lowe  in  Z.  Elektrochem.,  1910, 
pp.  1393  et  seq.1  It  aims  at  replacing  Lord  Rayleigh's  method 
of  measuring  the  refraction,  where  the  changes  in  the  composi- 
tion of  the  gas  to  be  examined  are  compensated  by  alterations 
of  its  pressure,  by  a  more  easily  manipulated  method,  which  is 
independent  of  the  thermometric  and  barometric  oscillations, 
and  admits  of  a  continuous  observation  of  the  composition  of  the 
gaseous  current.  This  object  has  been  attained  by  combining 
with  the  instrument  an  optical  compensator,  which  renders  the 
manipulation  extremely  simple,  the  only  part  to  be  moved 
being  the  measuring  screw  of  the  compensator.  It  can  be 
adapted  to  very  different  degrees  of  accuracy,  according  to  the 
requirements  of  the  case  ;  up  to  ^  per  cent,  of  CO2  in  the  air  of 
pits,  etc.  We  must  refer  for  the  details  to  the  original,  and  we 
only  mention  that  the  principal  applications  for  which  this 
instrument  is  intended  are  the  examination  of  the  air  of  coal- 
pits, of  the  purity  of  the  hydrogen  intended  for  aeronautic 
purposes,  of  coal-gas  carburetted  with  benzol,  of  the  percentage 
of  ammonia  in  air  obtained  by  synthetical  processes,  of  the  CO2 
and  SO2  in  smoke-gases.  Ottomar  Wolff  (Chem.  Zeit.,  1914, 
p.  349)  points  out  some  precautions  to  be  taken  in  gauging 
gas-interferometers. 

Mohr  (Z.  angew.  Chem.,  1912,  pp.  1313  et  seq^}  has  made 
an  investigation  of  the  application  of  the  interferometer  for  the 
technical  examination  of  smoke-gases,  and  found  it  useful  for 
that  purpose,  more  especially  for  the  estimation  of  carbon 
dioxide,  but  not  so  much  for  that  of  carbon  monoxide. 

Gas-analysis  by  positive  rays  has  been  proposed  by  J.  J. 
Thomson,  and  by  J.  E.  Verschaffelt  (Bull.  Soc.  Chim.  Belg., 
13>  P-  52)-  This  method  does  not  belong  to  the  domain  of 
technical  gas-analysis. 

Marc  Landau  (Comptes  rend.,  civ.  p.  403)  employs  the 
energy  of  light  for  gas-analysis,  especially  for  polymerising  non- 
saturated  hydrocarbons,  e.g.,  ethylene  and  acetylene.  The 
gaseous  mixture  is  exposed  to  ultra-violet  rays,  and  the 
contraction  of  volume  is  measured.  In  the  presence  of  oxygen 
the  energy  of  light,  such  as  that  of  a  mercurial  vapour  quartz 

1  It  can  be  obtained  from  Carl  Zeiss  in  Jena. 

M 


178  TECHNICAL  GAS-ANALYSIS 

lamp,  converts  substances  containing  carbon  and  hydrogen  into 
carbon  dioxide  and  water. 

The  application  of  acoustical  methods  for  the  detection  of 
small  quantities  of  methane  in  the  air  of  pits,  etc.,  will  be 
described  later  on  sub  "  methane." 

V.  SEPARATION  OF  GASES  BY  Low  TEMPERATURES. 

Methods  for  this  pupose  have  been  worked  out  by  Ramsay 
and  Travers  (Travers,  The  Experimental  Study  of  Gases) ;  by 
Hempel  (Gasanal.  Methoden^  4th  ed.,  p.  119);  by  Erdmann 
(Berl.  Ber.,  1910,  p.  1702). 

Lebeau  and  Damiens  (Comptes  rend.^  clvi.  p.  797  and  clvii. 
p.  144;  Am.  Abstr.,  1913,  p.  2109)  effect  the  analysis  of 
illuminating  gas  by  subjecting  the  gas  to  low  temperatures 
produced  by  means  of  liquid  air,  or  of  solid  carbon  dioxide  and 
acetone,  or  of  petroleum  spirit  cooled  by  liquid  air,  and  thus 
freezing  out  the  condensable  gases :  carbon  dioxide,  aqueous 
vapour,  the  saturated  homologues  of  ethane,  ethylene,  and 
acetylene ;  the  non-condensable  residue  consists  of  hydrogen, 
methane,  carbon  monoxide,  nitrogen,  and  oxygen.  Each 
fraction  is  then  submitted  to  a  process  of  extraction  or  frac- 
tionation.  The  determination  of  nitrogen  is  direct,  not  by 
difference.  As  much  as  1000  litres  of  gas  was  taken  for  a 
single  analysis,  and  this  method  is  asserted  to  admit  of  the 
most  complete  analysis  of  illuminating  gas  ever  made.  This 
method  is  highly  commended  by  Czako  (J.  Gasbeleucht.,  1913, 
p.  1192).  By  this  process  hydrogen  cannot  be  separated  from 
methane,  but  from  ethane,  propane,  etc. 

VI.  ESTIMATION  OF  THE  SPECIFIC  GRAVITY  OF  GASES. 

In  many  cases  the  specific  gravity  of  gaseous  mixtures 
admits  of  drawing  a  conclusion  as  to  their  composition.  In 
the  manufacture  of  illuminating  gas,  for  instance,  where  in  the 
different  stages  of  the  process  very  different  products  are 
formed,  the  specific  gravity  is  checked  throughout.  It  can 
also  be  made  available  for  checking  the  quality  of  furnace- 
gases,  of  pyrites-kiln  gases,  and  similar  cases. 

In  all  well-conducted  coal-gas  works  a  continuous  record 
of  the  specific  gravity  of  the  gas  produced  is  made,  which  is 


SPECIFIC  GRAVITY  179 

not  merely  of  statistical  value,  but  also  gives  some  information 
concerning  changes  in  the  composition  of  the  gas.  It  must, 
however,  be  borne  in  mind  that  changes  in  the  specific  gravity 
of  the  gas  are  no  certain  indication  of  its  quality.  Thus,  for 
instance,  the  specific  gravities  of  ethylene  and  of  nitrogen  are 
almost  identical. 

Apart  from  affording  indications  as  to  the  chemical  com- 
position, a  constant  check  of  the  specific  gravity  of  illuminating 
gas  is  important  for  the  manufacturing  process,  because  the 
quantity  of  gas  issuing  from  a  small  orifice  at  constant  pressure 
(as  in  the  Welsbach  burner)  varies  indirectly  with  the  square 
root  of  its  specific  gravity,  and  the  same  holds  good  with  regard 
to  the  capacity  of  the  mains  for  the  delivery  of  gas  under 
constant  pressure.  This  is  sometimes  noticed  in  a  very 
disagreeable  manner  when  changing  the  gas  supply  from 
ordinary  coal-gas  to  water-gas,  their  specific  gravities  differing 
so  very  much,  say  about  0-65  the  former  and  0-38  the  latter. 
Where  districts  of  very  different  level  have  to  be  supplied, 
it  must  be  also  taken  into  account  that  the  relative  pressure 
of  gas  increases  with  increasing  altitude,  the  increase  being 
greater  the  lower  the  specific  gravity  of  the  gas. 

In  the  use  of  coal-gas  for  the  filling  of  balloons,  its  specific 
gravity  is,  of  course,  of  primary  importance. 

(a)  Calculation  of  the  Specific  Gravity  from  the  Analysis. 

The  specific  gravity  of  a  gaseous  mixture  can  be  calculated 
from  the  analysis  by  multiplying  the  percentage  content  of 
the  single  gases  with  their  specific  gravities,  and  dividing  the 
sum  by  100,  according  to  the  formula : 

o.o696H2  +  0.967300  +  o.5538CH4  +  i.oCwH2n  +  2.8CnH2,l_6  + 
i.52oiCO2+i.io55O2  +  o.968oN2)  -— . 

This  presupposes  a  knowledge  of  the  composition  of  the 
gas.  Hence  it  is  mostly  necessary  to  employ  one  of  the  other 
methods  for  estimating  the  specific  gravity.  But  if  this  is  known, 
the  formula,  according  to  Pfeiffer,  may  render  valuable  service 
for  estimating  the  specific  gravity  of  the  total  heavy  hydrocarbons 
(CWH;J,  and  further  the  volume-percentage  of  benzene  and 
the  caloric  value.  If  we  signify  by  S  the  experimentally  found 


180  TECHNICAL  GAS-ANALYSIS 

specific  gravity  of  the  total  gas,  and  by  s  the  specific  gravity 
of  the  heavy  hydrocarbons,  we  have  : 

s  =  [1008 -(o-o696H2  + 0-967300  +  o-553SCH4  +  i-52oiCO2  4- 


For  instance  :  — 

Per  cent,  by  vol.  Sp.  gr. 

H2     =  SS'S   x  0-0696  .  .  .  3-861 

CO    =    8-4   x  0-9673  .  .  .  8-102 

CH4  =  29-7   x  0-5538  .  .  .  16-400 

CO2  =    1-7   x  1-5201  .  .  .  2-583 

O2     =    0-19x1-1055  .  .  .  0-2-10 

N2     =     1-2   x  0-9680  .  .  .  1-161 

32-3I7 

Specific  gravity  of  the  gas  (S)        .  *      03855 

Percentage  of  CnHm  .  .  3-3 

Hence  5=38-55  -32-32     .  .  .      I>888 

3'3 

For  accurate  determinations,  the  well-known  method  of 
Dumas  (directly  weighing  the  gas  in  glass  vessels  of  known 
capacity)  can  be  employed.  For  technical  purposes,  however, 
simpler  methods  are  used  which  will  now  be  described. 


(b)  Determination  of  the  Specific  Gravity  of  a  Gas  by  measuring 
its  Velocity  when  issuing  from  an  Orifice  (Apparatus  of 
Schilling}. 

This  method,  devised  by  Bunsen  (Gasometrische  Methoden, 
2nd  ed.,  1877,  p.  184),  is  founded  on  the  different  rates  of 
effusion  of  equal  gas  volumes  through  a  fine  opening,  the  squares 
of  the  time  of  effusion  showing  the  relation  of  the  specific 
gravities.  If  a  gas  of  specific  gravity  s  has  the  time  of  effusion 
/,  and  another  gas  of  specific  gravity  sl  the  effusion-time  t^ 
the  relation  is  : 

£L.-i 

When  comparing  a  special  gas  with  air,  as  is  always  done 
in  practical  work,  the  specific  gravity  s  of  the  air  is  put=i, 
and  is  thus  eliminated  from  the  calculation.  If  the  time  of 


SPECIFIC  GRAVITY 


181 


effusion  of  the  other  gas  is=£-  seconds,  and  that  of  an  equal 
volume  of  air  =  /  seconds,  the  specific  gravity  of  the  other 
gas  is  found  by  the  formula  : 


The  apparatus  employed  by  Bunsen  is  too  delicate  for 
technical  work,  but  its  principle  has  been  made  use  of  by 
H.  N.  Schilling  (Handb.  d.  Steinkohlengasbeleuchtung,  3rd  ed., 
p.  100),  whose  apparatus  is  so  con- 
venient that  it  has  found  universal 
application,  not  merely  for  coal-gas,  but 
also  for  all  other  gases  or  gaseous 
mixtures  sparingly  soluble  in  water. 

Schilling's  apparatus,  shown  in  Fig. 
83,  consists  of  a  glass  cylinder  B,  40 
mm.  wide  inside  and  450  mm.  high.  Its 
upper  end  is  cemented  into  a  brass 
cover  through  which  passes  the  inlet- 
pipe  a  ;  the  outlet-pipe  b  passes  through 
the  centre  of  the  cover.  Pipe  a  is  a 
brass  tube  3  mm.  wide,  turning  on  the 
outside  in  a  right  angle  and  provided 
with  a  stopcock  ;  it  is  connected  with 
the  source  of  the  gas  by  a  rubber  tube. 
The  outlet-pipe  b  is  12  mm.  wide,  and 
is  closed  at  the  top  by  a  disc  of  thin 
platinum  foil  r,  in  the  centre  of  which 
a  small  hole  has  been  made  by  means 
of  a  very  fine  needle  and  afterwards 
hammered  out,  thus  forming  the  orifice 
for  the  issuing  of  the  gas.  To  protect  it 
from  dust,  a  cap  is  screwed  on  c  when 
the  apparatus  is  not  in  use.  Tube  b 
can  be  shut  by  a  three-way  tap,  between 
the  orifice  and  the  cylinder,  which  can 

be  turned  so  as  to  communicate  either  with  b  or  c.  The 
outer  cylinder  A,  125  mm.  wide,  is  filled  with  water  nearly  up 
to  the  top,  when  the  inner  cylinder,  filled  with  gas,  is  immersed 
in  it.  This  height  of  water  is  shown  by  a  mark  on  the  glass. 


182  TECHNICAL  GAS-ANALYSIS 

The  inner  cylinder  B  has  two  marks,  m  and  n,  running  all 
round,  300  mm.  distant  from  each  other,  m  being  60  mm. 
distant  from  the  bottom  of  cylinder  B.  This  cylinder  is 
open  at  the  bottom,  resting  on  a  metal  foot,  and  is  kept 
in  position  at  the  top  by  a  metal  frame  r>  which  rests  with 
three  arms  on  the  rim  of  cylinder  A  and  also  carries  the 
thermometer  /. 

To  make  a  determination,  A  is  filled  with  so  much  water 
that  there  is  just  sufficient  room  for  introducing  cylinder  B 
when  filled  with  air.  As  soon  as  the  water  has  come  to  rest, 
the  time  of  effusion  of  the  volume  of  air  between  the  marks 
m  and  n  is  determined.  (According  to  Pannertz,  bands  of 
fine  card  round  the  marks  permit  of  greater  accuracy  of 
observation.)  The  stopcock  on  b  is  first  turned  so  as  to 
communicate  with  the  head  c\  the  level  of  the  water  in  the 
lower  part  of  the  cylinder  B  then  begins  to  rise,  displacing  the 
air,  and  the  time  is  taken  with  a  stop-watch  as  soon  as  the 
meniscus  passes  the  mark  m ;  another  reading  is  taken  when 
the  meniscus  of  water  passes  «,  and  the  time  between  the  two 
readings  is  noted.  The  residual  air  in  B  is  then  displaced  by 
the  gas  to  be  examined  by  connecting  stopcock  a  with  the 
supply,  and  opening  b ;  the  gas  is  allowed  to  pass  through  for 
about  two  minutes.  The  displacement  of  the  air  is  accelerated 
by  slowly  raising  B  almost  completely  out  of  the  water  and 
lowering  it  again.  The  outlet  of  b  is  then  closed,  B  is  again 
raised  to  fill  it  completely  with  gas,  the  inlet  of  a  closed,  and 
B  again  placed  in  position.  After  the  water  has  come  to  rest, 
the  time  of  effusion  of  the  gas  is  measured  under  exactly  the 
same  conditions  as  with  the  air  so  that  the  time  of 
effusion  of  equal  volumes  of  air  and  gas,  contained  between 
m  and  n  is  ascertained.  The  calculation  of  the  specific  gravity 
is  then  made  by  the  formula  given  above. 

As  the  air  and  gas  are  both  measured  in  a  state  saturated 
with  moisture  and  at  the  temperature  of  the  water  by  which 
they  are  confined,  all  corrections  with  respect  to  vapour  tension 
and  temperature  are  obviated.  It  is  well,  however,  to  read 
the  temperature  by  the  thermometer  t  before  and  after  the 
experiment,  as  a  check.  For  exact  work  the  test  should  be 
repeated ;  the  times  observed  in  the  duplicate  tests  should  not 
differ  from  each  other  by  more  than  0-2  second. 


LUX'S  GAS-BALANCE  183 

The  following  is  an  example  of  the  determination  of  the 
specific  gravity  of  coal-gas  : — 

Time  of  effusion  observed  for  gas  =  2'  25.1"  =  145-1" 
„  „  air    =  3'  40.8"  =  220.8" 

Specific  gravity  =-  \  ^^  =  0-4321. 


In  order  to  avoid  this  rather  troublesome  calculation,  Krug, 
at  the  suggestion  of  Pfeiffer  (/.  Gasbeleucht.,  1903,  p.  451),  has 
drawn  up  a  table  of  co-ordinates  which  permits  a  direct  reading 
of  the  specific  gravity  from  the  times  of  effusion  (obtainable 
from  Messrs  Oldenbourg  of  Munich). 

The  results  obtained  with  Schilling's  apparatus  are  reliable 
to  the  third  decimal  place,  and  this  method  is  always  to  be 
preferred  when  accuracy  is  important,  as,  for  example,  in  the 
calculation  of  the  calorific  value  from  the  analysis. 

A  "specific-gravity  bell,"  depending  on  the  same  principle 
as  the  above  apparatus,  is  made  by  Messrs  A.  Wright  &  Co., 
Westminster.  Other  apparatus  on  the  same  principle  are 
described  by  Gulich  (/.  Gasbeleucht.,  1911,  p.  699);  Felix  Meyer 
(Ger.  P.  appl.  M,  47821;  Z.  angew.  Chem.,  1913,  p.  121); 
A.  R.  Myhill  (Gas  World,  Iviii.  p.  763). 

An  apparatus  for  estimating  the  density  of  gases  on  the 
principle  employed  by  Bunsen  and  Schilling,  used  in  the 
laboratory  of  the  Karlsruhe  Technical  Laboratory,  is  described 
by  Hofsass  in  /.  Gasbeleucht.,  1913,  p.  871  ;  Chem.  Zentralb.  1913, 
ii.  p.  4353;  /.  Chem.  Soc.  Abstr.,  1913,  ii.  p.  1026.  The  same 
apparatus  can  also  be  utilised  for  testing  the  viscosity  (internal 
friction)  of  the  gas.  It  is  sold  by  C.  Desaga  of  Heidelberg. 

(c)   The  Gas-Balance  of  Lux. 

This  apparatus,  described  in  J.  Gasbeleucht.,  1887,  p.  251, 
is  very  much  employed  in  the  daily  practice  of  gas-works, 
as  it  indicates  the  specific  gravity  of  the  gas  directly.  It 
depends  upon  the  simple  principle  of  directly  weighing  equal 
volumes  of  air  and  gas,  the  difference  of  which  in  weight  is 
shown  as  specific  gravity  (air  =  i)  by  the  displacement  on 


184 


TECHNICAL  GAS-ANALYSIS 


a  scale.  The  globe-shaped  receiver,  Fig.  85,  which  may  be 
made  of  glass,  balances  with  the  beam  on  two  steel  points 
s  slt  Fig.  84,  which  move  in  a  hollow,  conical  steel  groove. 
The  fork-shaped  end  of  the  pillar  carries  the 
gas  inlet  r  and  outlet  oy  which  communicate 
|7t,  with  the  small  cups  /  and  pv  which  are  filled 
with  mercury.  Two  small  tubes  are  attached 
to  the  beam  of  the  balance  at  right  angles  to 
the  plane  of  swing,  the  ends  of  which  are  bent 
at  right  angles  and  are  connected  with  the 
inlet  and  outlet  of  the  pillar  by  the  mercury 
seal  of  the  cups  p  and  pv  without  interfering 
with  the  movement  of  the  beam.  One  of  the  small  tubes 
conducts  the  gas  into  the  globe  through  a  central  tube,  whilst 
the  other  serves  as  the  exit-tube. 


FIG.  85. 

The  balance  is  mounted  in  a  glass  case  provided  with  a 
door.  The  gas  inlet  and  outlet  to  r  and  o  are  connected  by  two 
small  tubes,  each  fitted  with  a  stopcock  and  rubber  connection 
on  one  of  the  ends  of  the  balance  case.  The  beam  of  the 
balance  is  divided  into  100  divisions,  and  from  each  10  to  the 


LUX'S  GAS-BALANCE  185 

next,  reckoned  from  the  pivot,  there  are  graduations,  0-0,0-1, 
0-2,  .  .  .  i-o;  the  beam  carries  a  nickel  rider.  The  graduated 
air  is  divided  into  50  parts,  the  middle  of  which  is  the  zero  ; 
the  graduations,  o-i,  0-2,  etc.,  are  placed  above  and  below  from 
each  10  to  the  next ;  the  marks  below  zero  are  negative 
values. 

The  balance  must  be  fixed  in  a  position  which  is  not  subject 
to  vibrations,  nor  exposed  to  direct  sunlight  or  other  sudden 
changes  of  temperature.  When  at  rest,  the  beam  of  the  balance 
rests  firmly  on  the  pillar  ;  it  is  released  by  means  of  a  screw  at 
the  right-hand  end  of  the  case.  When  the  globe  is  filled  with 
air  and  the  rider  is  on  the  outermost  mark  r,  the  pointer  should 
come  to  rest  exactly  on  the  zero  mark. 

The  adjustment  of  the  balance  beam  is  effected  by  means 
of  a  small  screw  above  the  middle  of  the  beam,  which  can  be 
moved  horizontally ;  for  further  adjustment,  the  rider  is  placed 
on  the  division  0-8.  If  the  balance  has  the  right  sensitiveness, 
each  degree  on  the  graduated  arc  should  correspond  to  each 
degree  on  the  beam  ;  the  pointer  ought  then  to  come  to  rest  at 
+  0-2  on  the  arc.  This  adjustment  is  made  by  means  of  the 
small  screw,  which  can  be  moved  vertically  over  the  middle  of 
the  beam. 

In  order  to  ascertain  the  specific  gravity  of  the  gas  to  be 
tested,  the  arc  is  first  displaced  from  the  balance  by  passing  the 
gas  through  for  five  minutes.  The  rider  is  then  placed  on  that 
point  of  the  graduation  which  is  regarded  as  likely  to  be 
nearest  to  the  specific  gravity  of  the  gas,  for  example,  0-4 ;  the 
beam  is  then  released  and  the  division  on  the  graduated  arc  on 
which  the  pointer  comes  to  rest  after  swinging  up  and  down  is 
read.  This  reading  added  to  or  subtracted  from  that  of  the 
rider  gives  the  second  decimal  for  the  specific  gravity ;  the  reading 
—  o-oi  would,  for  instance,  indicate  a  specific  gravity  of  0-40  — 
o-oi  =  0-39.  The  third  decimal  place  can  be  estimated  by  the 
eye ;  a  greater  degree  of  accuracy  in  the  determination  is  not  to 
be  expected. 

A  table  of  corrections  for  barometric  pressure  and  tempera- 
ture is  provided  for  the  apparatus,  which  influences  the  results 
to  the  fourth  place  of  decimals.  A  correction  of  this  kind  is 
theoretically  necessary  on  account  of  the  nature  of  the  balance. 
If,  for  example,  the  atmospheric  pressure  increases,  the  gas  in 


186  TECHNICAL  GAS-ANALYSIS 

the  globe  of  the  balance  as  well  as  the  surrounding  air  is 
contracted,  so  that  the  weight  of  the  contents  of  the 
globe,  and  that  of  the  air  displaced  thereby,  both  increase  ; 
accordingly  the  globe  of  the  balance  tends  to  become  heavier 
by  the  increasing  weight  of  the  gas,  and  lighter  in  proportion  to 
the  greater  upward  push  of  the  air.  The  absolute  increase  in 
weight  is  greater  in  the  case  of  air  than  in  that  of  gas,  in 
proportion  to  the  difference  in  their  specific  gravities ;  therefore 
the  globe  containing  the  gas  becomes  relatively  lighter  with  an 
increase  in  pressure,  and  heavier  with  a  decrease  in  pressure. 
The  necessary  correction  for  the  influence  of  changes  of  pressure 
is  to  add  0-0007  mm-  of  pressure  over  760  mm.,  and  to  subtract 
0-002  for  every  degree  above  15°,  and  vice  versa. 

For  example,  the  specific  gravity  of  a  gas  was  found  by  the 
balance  to  be  +0-41  at  28°  and  775  mm.  pressure : 

775-760=  15;  +0-0007x15       .  .      +0-0105 

28-15  =  13  >  -0-002x13  .  .      -0-0260 

-0-0155 
Corrected  sp.  gr.  0-41-0-0155        .  .          03945 

A  table  supplied  with  the  apparatus  gives  the  corrections 
from  o°  to  30°  C,  and  from  730  to  790  mm. ;  it  is,  however, 
applicable  only  to  gases  of  a  sp.  gr.  between  0-4  and  0-5. 

For  rapid  tests  following  closely  upon  each  other,  the 
apparatus  gives  satisfactory  results  to  the  second  decimal  place ; 
after  any  considerable  interval,  however,  say  from  one  day  to 
another,  a  new  adjustment  will  be  necessary,  as  a  rule,  on 
account  of  the  unequal  expansion  of  the  dissimilar  arms  of  the 
beam  with  changes  of  temperature,  for  which  no  compensation 
is  provided. 

The  apparatus  described  by  Chandler  (/.  Gas  Lighting^ 
cxvii.  p.  26)  is  essentially  a  Lux  gas-balance.  On  the  same 
principle  Arndt's  "  Econometer  "  is  constructed. 

(d)  Other  Apparatus  for  determining  the  Specific  Gravity 

of  Gases. 

Krell  (/.  Gasbeleucht.,  1 899,  p.  212)  has  devised  an  apparatus 
for  determining  the  specific  gravity  of  gases  by  measuring,  with 
a  delicate  differential  pressure  gauge,  the  difference  between 


SPECIFIC  GRAVITY  187 

the  statical   pressure  of  a   long   vertical   column   of  gas   and 
a  column  of  air  of  equal  length. 

Threlfall  (Proc.  Roy.  Soc.,  A.,  1906,  p.  542  ;  /.  Soc.  Chem.  Ind., 
1897,  p.  359)  has  indicated  an  apparatus  on  the  same  principle. 

Other  apparatus  have  been  devised  by  Pannertz  (/. 
Gasbeleucht.,  1905,  p.  901);  Knoll  (Ger.  P.  247738);  Simmance 
and  Abady  (B.  P.  27484  of  1911  ;  Ger.  P.  266538);  Dosch  (Ger. 
P.  242704) ;  Shaffner  (Amer.  P.  1065974) ;  G.  E.  Wolf  (Fr.  P. 
456295  and  Ger.  P.  268352;  Z.  angew.  Chem.^  1904,  ii.  p.  10)  ; 
Kalahne  (Ger.  P.  268353);  Burkhardt  (Ger.  Ps.  262867  and 
266679)  ;  Contzen  ("  Hydro  "-Apparatus  sold  by  J.  von  Geldern 
&  Co.,  DiisseldorfT) ;  Hofsass  (/.  Gasbeleucht.,  1913,  Ivi.  p.  841); 
Aston  (Proc.  Roy.  Soc.,  1914,  p.  439);  Bomhard  and  Konig 
(Ger.  P.  269862). 

Estimation  of  the  Specific  Gravity  of  Gases  in  Motion. — Fel. 
Meyer  (Ger.  P.  258858)  drives  the  gas  to  be  examined,  mixed 
with  a  gas  of  known  composition,  or  else  the  latter  mixed  with 
the  former,  through  measuring-apparatus  gauged  for  the  density 
of  the  gas,  by  which  the  velocity  of  the  current  or  the  quantity 
of  the  gas  is  measured,  and  the  specific  gravity  of  the  gas  is 
read  off.  He  calls  this  instrument  "  Rotameter."  Preferably 
two  similar  measuring  devices  connected  by  a  long  tube  are 
used.  The  whole  is  filled  with  the  gas  under  examination,  and 
a  gas,  e.g.  air  of  known  specific  gravity,  is  passed  into  the  first 
measuring  device,  thus  causing  an  equal  quantity  of  the  gas 
under  examination  to  pass  through  the  second  measuring 
device.  In  this  way  the  first  measuring  device  indicates  the 
velocity  of  the  known  gas,  and  hence  also  of  the  gas  under 
examination,  whilst  the  specific  gravity  of  the  latter  can  be 
ascertained  from  the  indication  of  the  second  measuring  device. 

Dosch  (Ger.  P.  242704)  places  within  a  case  containing  the 
gas  and  closed  (except  the  pipes  for  the  entrance  and  the  exit 
of  the  gas)  a  revolving  wheel  (a  "  flying  pinion  "),  and,  at  different 
distances  from  the  axis  of  the  latter,  two  pipes  leading  to  one  or 
two  differential  pressure  gauges,  thus  utilising  the  statical  or 
the  velocity  pressure  for  estimating  the  specific  gravity  of  the 
gas.  Special  openings  in  the  entrance  and  exit  pipes  permit  of 
altering  the  difference  of  pressure  at  the  same  time  of  revolu- 
tions of  the  wheel,  and  increasing  the  exactness  of  the 
indications  with  the  same  pressure  gauge.  On  the  axis  of  the 


188  TECHNICAL  GAS-ANALYSIS 

wheel  another  equal  wheel  may  be  fixed,  which  turns  within 
a  case  filled  with  a  gas  serving  for  comparison,  thus  doing 
away  with  the  necessity  of  a  special  counter  for  the  number  of 
revolutions.  This  apparatus  may  be  used  for  the  continuous 
estimation  of  hydrogen  in  producer-gases. 

Chabaud,  in  his  Ger.  P.  264714,  describes  an  apparatus  for 
the  continuous  indication  of  the  specific  gravity  of  gases  in 
motion  by  means  of  a  float,  which  is  kept  in  suspension  by  the 
gases,  and  which  admits  of  reading  the  specific  gravity  at  a 
graduated  pipe  without  any  manipulation. 

VII.  MEASUREMENT  OF  PRESSURE  AND  OF  DRAUGHT. 

For  the  technical  analysis  of  gases,  in  many  cases  the 
pressure  of  a  current  of  gas  must  be  determined,  apart  from  the 
necessity  of  observing  such  pressures  for  properly  carrying  out 

manufacturing  processes.     This 
subject   is   treated   in  detail  in 
Lunge's    Technical  Methods   of 
£,  Chemical  A  nalysis,  translated  by 

C.  A.  Keane,  vol.  i.  pp.  165  et 
seq.   (1908);    in    this    place   we 
A  shall  merely  give  an  outline  of 

I  II  I  II        !t 

Instruments  which  measure 

the  statical  difference  of  pressure, 
say,  between  the  inside  of  an 
apparatus  and  the  outer  atmo- 
sphere,  are  called  Pressure  Gauges 
or  Manometers.  Those  which 

measure  dynamic  differences,  registering  directly  the  velocity  of 
a  current  of  gas,  are  called  Anemometers. 

For  many  purposes,  where  only  small  differences  of  pressure 
have  to  be  measured,  it  is  sufficient  to  employ  |J-tUDes  A,  B, 
Fig.  86,  provided  with  a  scale  C.  The  limb  A  is  connected 
with  the  tube  D,  which  passes  through  the  wall  E  of  the 
apparatus  in  which  the  gas  is  contained  ;  the  other  limb  B  is 
open  to  the  outside  air.  If  the  pressure  within  the  apparatus  is 
greater  than  that  of  the  outside  air,  the  liquid  will  stand  at 
a  higher  level  in  B  than  in  A,  and  inversely.  A  pressure  of 


MANOMETERS 


189 


01    mm.  of  water   corresponds    to  a    velocity    of  the   gas    of 
1-23  metres  per  second. 

Such  small  differences  of  pressure  are  more  accurately 
measured  by  Peclet's  pressure  gauge  shown  in  Fig.  87.  It 
consists  of  a  bottle  A,  with  a  neck  near  the  bottom  which  is 
connected  with  the  slightly  inclined  tube  B,  2  or  3  mm.  wide, 
provided  with  a  scale.  B  is  fixed  to  a  vertical  board,  provided 
with  a  spirit  level.  The  liquid,  either  water  or  preferably 
alcohol,  forms  a  very  long  meniscus  in  B.  If  B  has  an  inclination 
of  i  in  25,  each  millimetre  on  this  tube  represents  a  difference 
of  pressure  of  YV  mm-  m  A.  If  the  scale  on  B  can  be  read  to 
0-5  mm.,  differences  of  0-2  in  pressure  can  be  measured.  The 
upper  portion  of  the  inner  walls  of  the  tube  B  should  be 


FIG.  87. 


moistened  before  each  test  by  inclining  the  instrument.  Alcohol 
is  preferable  to  water,  both  on  account  of  its  smaller  coefficient 
of  friction,  and  because  it  returns  more  quickly  to  its  original 
position  ;  but  the  pressures  must  then  be  corrected  according 
to  the  specific  gravity  of  the  alcohol.  If  this  is  =  0-800,  I  mm. 
corresponds  to  O-8  mm.  of  water  pressure. 

Differential  manometers  are  those  where  two  non-miscible 
liquids  are  employed  in  (J -tubes  or  similar  apparatus.  To  this 
class  belong  the  instruments  designed  by  Seger  (described  in 
Lunge-Keane,  i.  p.  167)  and  Konig  (ibid.,  p.  168).  Langen's 
manometer  (ibid.,  p.  169)  employs  a  combination  of  two  tubes 
of  unequal  diameter. 

In  the  same  place  (pp.  169  et  seq.)  the  method  of  calculating 
the  velocity  of  a  current  of  gas  from  the  manometric  pressure 
by  Peclet's  formula  is  explained,  and  Fletcher's  anemometer, 
modified  by  Lunge,  is  described,  which  utilises  this  method  for 
practical  purposes.  There  also  tables  are  given  for  reducing 


190  TECHNICAL  GAS-ANALYSIS 

the  anemometer  readings  to  velocity  of  current  expressed  in 
feet  or  metres  per  second. 

An  apparatus  for  determining  the  composition  and  velocity 
of  gas  mixtures  is  described  in  W.  Heckmann's  Ger.  Ps.  252538 
and  259600.  The  gas  is  led  into  a  throttle  chamber  connected 
with  a  differential  pressure  gauge,  and  an  absorbing  liquid  is 
sprayed  into  the  chamber,  or  contained  in  a  separate  vessel, 
so  that  the  pressure  gauge  registers  not  only  the  pressure 
corresponding  to  the  velocity  of  the  gas  mixture,  but  also  the 
diminution  of  pressure  caused  by  the  absorption  of  one  of  the 
constituents. 

Verbeck's  "  Precision-differential  manometer "  and  "  Pre- 
cision-control-manometer "  for  testing  the  draught  and  velocity 
of  gases  are  described  in  Chem.  Zeit.,  1913,  p.  1361. 

Liitke  (Stahl  u.  Risen,  xxxiii.  p.  1307)  describes  new 
instruments  for  measuring  the  pressure  and  velocity  of  gas 
and  steam.  The  apparatus  consists  of  a  long  pointer  pivoted 
a  short  distance  from  one  end.  On  one  side  of  the  pivot  is 
suspended  from  the  pointer  a  small  bucket  carrying  mercury, 
and  on  the  other  side  is  suspended  a  weight  which  serves  to 
balance  the  pointer  in  a  horizontal  position.  Into  the  mercury 
bucket  dips  one  end  of  an  inverted  U~tut>e,  the  other  end  of 
which  is  connected  with  the  bottom  of  the  receiver.  The  tube 
acts  as  a  syphon,  and  under  normal  conditions  the  pointer 
is  balanced  with  the  mercury  in  both  receiver  and  bucket  at 
the  same  level.  Through  the  sealed  top  of  the  receiver  a  tube 
passes  to  the  pipe  in  which  the  pressure  is  to  be  measured. 
The  pressure  or  suction  in  the  pipe  forces  mercury  from  the 
receiver  into  the  bucket,  or  vice  versa,  thus  causing  the  pointer 
to  move  up  or  down.  With  proper  calibration  the  instrument 
thus  makes  a  direct  record.  For  measuring  a  difference  in 
pressure,  it  is  necessary -to  have  two  sets  of  mercury  buckets 
and  receivers. 

VIII.   DETERMINATION  OF  THE  CALORIFIC  VALUE  OF  GASES. 

The  calorific  power  of  gaseous  mixtures  is  of  extreme 
importance  for  their  technical  uses.  This  holds  good,  not 
merely  of  gaseous  mixtures  intended  from  the  outset  for 
heating  purposes,  such  as  producer-gas,  water-gas,  etc.,  but 


CALORIFIC  VALUE  191 

nowadays  also  for  coal-gas  (illuminating  gas),  not  merely  on 
account  of  its  use  for  heating  domestic  stoves,  etc.,  but  even 
in  connection  with  its  illuminating  properties  (which  are  not 
treated  in  this  book,  but  for  which  we  refer  the  reader  to  the 
article  on  "  Illuminating-Gas  and  Ammonia,"  in  vol.  ii.  of  Lunge's 
Technical  Methods  of  Chemical  Analysis,  translated  by  Keane, 
vol.  ii.  pp.  697  et  seq.\  since  the  Auer-Welsbach  process  and 
other  processes  for  incandescent  burners  have  spread  all  over. 
It  is  estimated  that  in  Great  Britain  not  more  than  10  per  cent, 
of  the  gas  for  illuminating  purposes  is  now  burned  in  open 
flames,  and  on  the  Continent  the  proportion  is  still  smaller. 

Whilst  the  illuminating  power  of  a  gas  is  not  an  absolute 
quality  of  it,  but  varies  greatly  with  the  construction  of  the 
burner  employed,  the  rate  at  which  the  gas  is^burned,  etc.,  etc., 
and  therefore  this  power  must  be  determined  under  certain 
specified  conditions,  varying  very  greatly  at  different  works, 
the  calorific  power  is  an  absolute  quality  of  the  gas,  representing 
its  total  potential  energy,  expressed  in  heat-units.  Provided 
that  the  combustion  is  complete,  the  calorific  power  remains 
the  same  whatever  burner  is  employed,  and  whatever  the  rate 
of  combustion. 

The  unit  of  heat  employed  for  calorific  determinations  in  Great 
Britain  is  the  British  Thermal  Unit  (usually  denoted  B.  Th.  U., 
to  distinguish  it  from  the  electrical  Board  of  Trade  Unit,  for 
which  the  contraction  B.  T.  U.  is  employed),  and  is  the  quantity 
of  heat  required  for  raising  I  Ib.  of  water  i°  F.  The  calorific 
power  of  a  gas  is  usually  stated  in  the  number  of  B.  Th.  U., 
evolved  in  the  combustion  of  I  cb.  ft.  of  the  gas.  On  the 
Continent,  the  heat  unit  employed  is  the  larger  caloric  (Cal.) 
and  the  results  are  stated  in  calories  per  cubic  metre.  The 
calorific  power  tests  of  London  gas,  carried  out  under  the 
instruction  of  the  Metropolitan  Gas  Referees,  are  recorded  in 
calories  per  cubic  feet. 

For  conversion  of  metrical  calories  into  B.  Th.  U.,  the  factor 
is  3-968 ;  that  for  converting  calories  per  cubic  metre  into 
B.  Th.  U.  per  cubic  foot  is  0-1124. 

In  the  determination  of  the  calorific  power  of  gases  con- 
taining hydrogen,  the  steam  produced  by  the  combustion  is 
condensed  to  liquid  water  in  the  calorimeter,  and  the  latent 
heat  of  such  steam  is  therefore  always  included  in  the 


192  TECHNICAL  GAS-ANALYSIS 

observed  calorific  power,  which  is  called  the  Gross  Calorific 
Power.  This  latent  heat  can,  however,  be  utilised  in  practice 
only  in  the  very  exceptional  cases  where  the  products  of  com- 
bustion are  completely  cooled  to  atmospheric  temperature. 
It  is,  of  course,  never  evolved  in  the  flame  itself,  and  takes  no 
part  in  the  development  of  the  flame  temperature ;  nor  is  it 
evolved  in  the  cylinder  of  a  gas-engine,  and  is  therefore 
unavailable  for  the  production  of  mechanical  energy.  As  the 
latent  heat  of  steam  is  known  =  0-537  cal-  or  2<I3  B.  Th.  U.  for 
each  cubic  centimetre  or  gramme  of  the  water  condensed,  this 
latent  heat  can  be  ascertained  by  collecting  and  measuring  the 
amount  of  water  obtained  during  the  test.  The  deduction  of 
this  amount  from  the  gross  value  gives  the  Net  Calorific 
Power. 

As  the  results  are  stated  per  unit  volume  of  the  gas,  it  is 
necessary  to  define  the  standard  temperature  and  pressure  at 
which  the  gas  is  measured.  In  Great  Britain  the  standard 
conditions  are  :  that  the  gas  shall  be  measured  in  the  moist  state, 
at  60°  F.  and  30  in.  pressure.  A  table  for  obtaining  the  volume 
of  a  gas  under  these  conditions,  from  its  volume  at  temperatures 
of  from  40°  to  80°  F.,  and  from  28-0  to  31  in.  pressure,  is  given 
in  Lunge-Keane's  book,  ii.  pp.  690-691.  In  Germany,  the 
results  are  sometimes  stated  for  dry  gas  at  o°  C,  and  some- 
times for  moist  gas  at  15°  C.  and  760  mm.  The  latter  conditions 
are  practically  identical  with  the  British  conditions  of  moist  gas 
at  60°  F.  and  30  in.,  and  considerable  confusion  is  often  caused 
thereby,  when  the  standard  conditions  are  not  specified. 

Abady  (/.  Gas  Lighting,  cxx.  p.  956)  points  out  that,  along 
with  determining  the  heating  value  of  coal-gas,  etc.,  the  specific 
gravity  of  the  gas  should  be  regularly  determined,  since  in 
this  manner  the  fluctuations  of  the  former  can  be  more  easily 
explained.  As  a  rule  the  heating  value  rises  in  the  same  ratio 
as  the  specific  gravity ;  still,  cases  occur  where  the  specific 
gravity  goes  up,  while  the  heating  value  goes  down.  This 
proves  that  either  the  percentage  of  carbon  dioxide,  or  that  of 
the  nitrogen,  or  both,  are  increasing,  and  corresponding  measures 
must  be  taken,  whereas  the  mere  determination  of  the  heating 
value  does  not  indicate  this.  The  same  author  later  on  (ibid.,  cxxi. 
p.  527)  recommends  for  the  examination  of  illuminating  gas, 
Simmance's  "total-heat  calorimeter,"  which  works  with  dried 


CALCULATION  OF  CALORIFIC  VALUE  193 

combustion  air,  and  is  therefore  independent  of  the  variations 
of  moisture  in  atmospheric  air. 

Calculation  of  the  Calorific   Value  of  Gaseous  Mixtures 
from  the  Analysis. 

For  this  purpose  we  must  start  from  the  scientifically  deter- 
mined calorific  values  of  the  single  constituents  of  the  gaseous 
mixture.  In  the  following  table  (IX. — A,  p.  194)  (from  Lunge- 
Keane,  vol.  ii.  p.  693)  the  gross  and  net  calorific  values  of  a  number 
of  gases  are  given  of  unit  volume  of  the  constituents  present  in 
any  quantity  in  ordinary  coal-gas,  both  in  Cal.  per  cubic  metre, 
and  B.  Th.  U.  per  cubic  foot.  Further,  in  each  set,  figures  are 
given  for  showing  the  values  at  (a)  o°  C.  and  760  mm.,  or  32°  F. 
and  30  in.  dry  ;  (£)  15°  C.  and  760  mm.,  or  60°  F.  and  30  in. 
dry;  and  (c)  I5°C.  and  760  mm.,  or  60°  F.  and  30  in.  moist. 
The  figures  in  the  table  are  calculated  from  the  observed 
calorific  power  of  known  weights  of  the  various  gases  and  their 
specific  gravities,  Thomsen's  values  being  employed  except  in 
the  case  of  benzene  vapour.  The  figures  found  for  the  latter 
by  Thomsen,  Berthelot,  and  Stohmann  vary  considerably,  and 
as  the  latter  approximates  to  the  average  of  all  the  values 
obtained,  it  has  been  taken  in  preference  to  Thomsen's 
figure. 

The  figures  given  for  the  net  values  in  the  table  are  obtained 
by  deducting  the  latent  heat  of  the  steam  produced  (0-537  cal. 
per  cubic  centimetre)  from  the  gross  figures.  In  calorimetric  tests 
it  is  usual  to  deduct  roundly  06  cal.  for  each  cubic  centimetre  of 
condensed  water,  which  includes  the  latent  heat  of  the  steam,  and 
also  approximately  the  sensible  heat  evolved  in  the  calorimeter 
by  the  cooling  of  the  condensed  water  from  100°  C.  to  ordinary 
temperature.  This  last  amount  should,  however,  not  be 
deducted,  if  the  net  thermodynamic  value  is  to  be  ascertained 
as  it  is  evolved  as  heat  in  the  flame,  and  contributes  to  the 
development  of  flame  temperature  and  of  mechanical  energy 
under  normal  conditions.  An  additional  table  (IX. — B)  is  given, 
showing  the  further  deductions  which  must  be  made  from  the 
net  values  given  in  the  first  table,  if  it  be  desired  to  allow  also 
for  the  sensible  heat  of  the  condensed  steam. 

From  the  value  of  the  constituents  given  in  the  table,  the 

N 


194 


TECHNICAL  GAS-ANALYSIS 


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CALCULATION  OF  CALORIFIC 


calorific  power  of  a  gaseous  mixture  may  be  calculated  by 
multiplying  the  percentage  of  each  constituent  by  its  calorific 
power,  and  dividing  the  sum  of  the  multiples  by  100,  as  shown 
in  the  following  example  : — 


C02 
CnH, 

02 
CO 
CH4 
H 


Per  cent, 
by  vol. 

Gross  cal.  power 
at  60*  F.  and 
80  in.  moist. 

Multiple. 

1-2 

X 

nil 

... 

3'4 

X 

2,319       = 

7,885 

°*3 

X 

nil 

... 

6-8 

X 

321       = 

2,183 

32-9 

X 

1,003       = 

32,999 

49-2 

6-2 

X 
X 

321       = 
nil 

15,791 

58,858-7-100  =  588-6 


The  calculated  calorific  power  of  such  a  sample  of  gas  is 
therefore,  588-6  B.  Th.  U.  gross  per  cubic  foot  measured 
moist  at  60°  F.  and  30  in. 

The  value  thus  obtained  is,  of  course,  subject  to  all  the 
errors  of  analysis,  and  a  further  possibility  of  error  arises 
from  the  uncertainty  as  to  the  exact  composition  of  the  heavy 
hydrocarbons,  CWHOT.  It  is  customary  to  assume  that  the 
mixture  of  these  has  the  same  calorific  power  as  propylene, 
as  has  been  done  above,  but  this  can  only  be  regarded  as 
an  approximation.  Usually,  however,  in  the  case  of  coal-gas, 
the  analyses  thus  calculated  agree  to  within  2  to  3  per  cent, 
with  the  figures  obtained  by  the  calorimeter.  With  carburetted 
water-gas,  in  which  a  much  higher  percentage  of  unsaturated 
hydrocarbons  is  present,  the  agreement  is  often  much  less 
satisfactory. 

If  the  percentages  of  ethylene  and  benzene  have  been 
determined  separately  by  any  of  the  methods  previously 
described,  these  figures  are  multiplied  by  their  respective 
calorific  powers,  instead  of  employing  the  propylene  values. 

The  application  of  the  values  of  the  composition  of  gases 
by  means  of  gas-analysis  to  the  calculation  of  their  calorific 
value  has  been  studied  experimentally  by  F.  S.  Wade  (/".  Gas 
Lighting,  1912,  cxx.  p.  518).  While  the  calorific  value  of 
ordinary  coal-gas  can  be  accurately  ascertained  from  its 
analysis,  in  the  case  of  oil-gas  the  calorific  values  calculated 


196 


TECHNICAL  GAS-ANALYSIS 


from  its  composition  is  always  lower  by  7  per  cent,  than 
that  found  in  the  calorimeter,  probably  owing  to  the  presence 
of  heavy  hydrocarbons  of  greatly  varying  composition. 


The  Direct  Measurement  of  the  Calorific  Power. 

In   place   of   the   indirect   and   tedious   estimation   of    the 
calorific    power    by   calculation    from    the    complete    analysis 

(which  frequently  is  not  available), 
this  value  is  now  nearly  always  ob- 
tained by  direct  measurement. 

The  calorimeters  in  use  for  esti- 
mations, in  which  large  volumes  of 
gas  are  available,  are  all  modifications 
of  the  calorimeter  devised  by  Hartley 
in  1882  (/.  Gas  Lighting,  1884,  p. 
1 142),  in  which  the  gas  is  burned 
at  a  constant  rate  in  a  chamber 
through  which  water  is  also  flowing 
at  a  constant  rate.  From  the  volume 
of  the  gas  consumed  and  of  water 
passed  in  a  given  time  through  the 
apparatus,  and  the  average  increase 
in  the  temperature  of  the  water,  the 
calorific  power  is  readily  calculated. 
The  amount  of  water  condensed  from 
a  given  volume  of  gas  also  supplies 
a  ready  means  of  ascertaining  the 
necessary  deduction  for  the  latent 
heat  of  water  required  to  determine 
the  net  calorific  power. 

(a)  Junckers*  Gas  Calorimeter. — In 
FIG.  88.  this  apparatus,  the  heat  generated  by 

the  flame  of  burning  gas  is  transmitted 

to  a  current  of  water  flowing  at  a  constant  rate,  and  measurements 
are  made  of  the  volume  of  gas  burnt,  the  quantity  of  water 
heated,  the  difference  in  temperature  of  the  water  on  entering 
and  leaving  the  apparatus,  and  the  quantity  of  water  condensed 
from  the  products  of  the  combustion.  The  gas  is  burnt  in 
a  large  Bunsen  burner  (Fig.  88)  in  the  combustion  chamber 


CALORIMETERS  197 

a,  which  consists  of  an  annular  copper  vessel,  the  annular  space 
being  traversed  by  a  number  of  upper  tubes  by  connecting  the 
top  with  the  bottom  of  the  chamber.  The  products  of  com- 
bustion pass  through  these  tubes  in  a  downward  direction,  the 
condensed  water  being  collected  at  <?,  and  the  waste  gases 
escaping  through  the  side-tube  d.  The  current  of  water  enters 
at  e,  where  it  passes  through  a  sieve  h,  and  enters  the  calori- 
meter through  g  and  z,  thus  circulating  in  an  opposite  direction 
to  that  of  the  products  of  combustion,  whereby  complete 
cooling  of  the  latter  to  the  temperature  of  the  water  is  effected. 
The  water,  after  passing  through  the  annular  chamber,  goes 
over  a  series  of  baffle  plates  at  m,  to  ensure  thorough  mixing, 
and  then  passes  out  though  the  overflow  z>  where  it  is  collected 
and  measured.  The  pressure  of  water  is  kept  constant  by  the 
two  overflows  at  h  and  #,  the  water  being  run  into  h  at  a  greater 
rate  than  it  passes  through  the  calorimeter ;  the  rate  of  flow  is 
regulated  by  the  cock  i.  The  temperature  of  the  entering 
water  is  taken  by  the  thermometer  k,  that  of  the  exit  water 
by  the  thermometer  above  m.  The  whole  instrument  is 
enclosed  in  a  cylindrical  air-jacket  of  polished  or  plated  copper 
to  prevent  radiation. 

The  whole  apparatus,  as  arranged  for  actual  experiment, 
is  shown  in  Fig.  89.  The  gas  to  be  tested  is  measured  in 
a  small  wet  meter,  provided  with  a  thermometer,  and  is  passed 
through  a  governor  to  ensure  a  steady  pressure  of  gas  at  the 
burner;  a  water-pressure  gauge  is  attached  to  the  governor, 
which  indicates  the  pressure,  above  that  of  the  atmosphere, 
at  which  the  gas  is  measured.  As  the  water  supply  may  vary 
considerably  in  temperature,  even  within  a  short  period  of 
time,  if  taken  directly  from  a  tap,  it  is  preferable  to  have 
a  large  reservoir  for  its  storage.  Pfeiffer  recommends  a  sheet- 
zinc  tank  of  60  litres  capacity  (H,  Fig.  89),  provided  with 
a  pipe  wt  which  serves  both  for  filling  and  discharging,  a  glass 
gauge  and  an  overflow  pipe  u ;  the  pipe  w  is  connected  with 
the  pressure  box  of  the  calorimeter  through  the  tap  v.  The 
experiment  should  be  so  regulated  that  the  temperature  of  the 
exit  gases  at  s  (Fig.  89)  is  the  same  as  that  of  the  laboratory, 
so  that  they  are  only  saturated  with  the  quantity  of  moisture 
corresponding  to  this  temperature.  Instead  of  measuring  the 
water  collected  from  <;,  Pfeiffer  prefers  weighing  it  in  the 


198  TECHNICAL  GAS-ANALYSIS 

bottle  F,  of  about  10  litres  capacity,  the  weight  of  the  empty 
bottle  having  been  previously  determined. 

The  condensed  water  from  the  calorimeter  is  collected  in 
the  measuring  cylinder  d  (Fig.  89),  which  is  placed  in  position 
after  the  gas-meter  index  has  completed  a  revolution,  from 


FIG.  89. 

the  start  of  the  experiment,  and  the  collecting  continued  for 
a  corresponding  period  after  the  bottle  F  has  been  removed. 

To  carry  out  a  test,  the  water  is  first  turned  on,  and  when 
it  is  running  from  both  overflows,  the  gas  is  lighted  and  the 


CALORIMETERS  199 

speed  of  the  water  regulated  by  the  cock  z,  so  that  there  is  a 
difference  of  from  10°  to  20°  between  the  inlet  and  outlet 
thermometers.  Illuminating  gas  is  burned  at  the  rate  of  from 
100  to  300  litres  (4  to  n  cb.  ft.)  per  hour,  hydrogen-gas 
from  200  to  600  litres,  producer-gas  at  the  rate  of  from  400 
to  1000  litres  (14  to  35  cb.  ft.).  When  the  difference  in 
temperature  of  the  two  thermometers  is  nearly  constant,  and 
the  condensed  water  is  dripping  regularly  into  d,  the  test  can 
be  begun.  This  is  done  by  waiting  until  the  gas-meter  index 
passes  any  desired  point,  and  then  quickly  introducing  the 
outlet  water  tube  c  into  a  suitable  measuring  vessel ;  a  series 
of  readings  of  the  thermometer  are  taken  whilst  about  28  litres 
(i  cb.  ft.)  of  gas  is  burnt,  and  the  volume  of  gas  and  of 
collected  water  measured.  The  inlet  thermometer  k  should  be 
read  every  minute,  and  the  outlet  thermometer  T  (Fig.  89) 
every  half  minute. 

The  calorific  value  is  : 

Weight  of  water  x  temperature  difference 
Volume  of  gas  consumed 

the  volume  of  gas  being  corrected  for  temperature  and 
pressure. 

The  value  thus  obtained  represents  the  calorific  power  of 
the  gas,  when  the  water  formed  by  the  combustion  is  converted 
into  the  liquid  state  in  the  calorimeter.  To  obtain  the  calorific 
value  when  the  water  formed  escapes  as  steam,  the  latent  heat 
of  the  condensed  water  must  be  deducted ;  the  quantity  of 
heat  evolved  by  each  cubic  centimetre  of  condensed  water  may 
be  taken,  with  sufficient  accuracy  for  most  purposes,  =0-6  cal. 
(i  cal.  =  the  amount  of  heat  required  to  raise  1000  g.  of  water 
i°  C.),  and  this  value,  multiplied  by  the  number  of  cubic  centi- 
metres of  water  condensed  and  divided  by  the  gas  consumed, 
will  give  the  total  heat  to  be  deducted  from  the  "gross" 
calorific  value  to  give  the  "  net "  calorific  value  of  the  gas,  with 
the  water  formed  in  the  combustion  remaining  as  steam.  The 
result  in  calories,  multiplied  by  3-97,  gives  the  calorific  value 
in  British  thermal  units. 

No  further  corrections  are  necessary,  and  the  results  are 
in  every  respect  satisfactory,  if  the  experimental  conditions 
are  properly  carried  out.  It  is  important  that  the  determina- 


200  TECHNICAL  GAS-ANALYSIS 

tions  should  be  made  in  a  room  free  from  any  considerable 
variation  of  temperature. 

If  a  larger  flame  is  used,  the  combustion  is  apt  to  be 
incomplete ;  F.  Fischer  accordingly  recommends  ascertaining 
by  a  preliminary  experiment  that  the  waste  gases  contain 
several  per  cent,  of  oxygen,  as  otherwise  the  result  may  be 
5  per  cent,  or  more  too  low. 

Example : 

Volume  of  gas  consumed  (5  revolutions  of  meter  index,  at 

3-06  litres  per  revolution)     .....        15.3  litres 

Weight  of  water  .  .  .  .  .  .        5310  g. 

Temperature  of  inlet  water,  constant     .  .  ,  .        13-8° 

„  outlet  water,  28-1,  28-15,  28-15,  28-1,  28-1,  28-1, 

28*1,28*1       ..          .  .  .  .  .          mean  28- 11° 

Difference  of  temperature  .  .  ...         14-31° 

Volume  of  condensed  water       .  .  -.  .  .         14  c.c. 

Temperature  of  room      .  .  .  .  .  .22° 

Barometer  .  .  ...  .  .        766  mm. 

Gross  calorific  value  per  cubic  metre,  at  I5°C  and  760  mm. 

=  5-3IQX  14*31  x273  +  22x76o  g2 

0-0153  288        7°° 

Net  calorific  value  per  cubic  metre,  at  I5°C  and  760  mm. 
-  (5-3IQXI4-30-Q-6XI4    273  +  22    760 
0-0153  288~X^66 

Pfeiffer  (J.  Gasbeleucht.,  1904,  p.  684)  regards  the  above 
method  of  calculating  the  net  calorific  value  as  somewhat 
inaccurate,  on  account  of  the  small  quantity  of  condensed 
water  collected  in  a  single  experiment.  As  the  result  of  his 
own  observations,  he  is  of  opinion  that  it  is  best  calculated 
from  the  gross  calorific  value  on  the  basis  of  independent 
experiments  in  which  50  to  70  c.c.  condensed  water  are 
collected.  From  numerous  determinations  he  finds  that  the 
net  value  is  n-i  per  cent,  less  than  the  gross  value  in  the 
case  of  gas  made  from  English  or  from  Westphalian  coal,  and, 
as  an  average,  8-6  per  cent,  less  in  the  case  of  carburetted 
water-gas.  From  these  data,  the  net  calorific  value  may  be 
calculated  directly  from  the  experimental  determination, 
without  reference  to  the  volume  of  condensed  water  formed. 
To  facilitate  the  correction,  Pfeiffer  has  constructed  a  table, 
which  is  reproduced  in  Lunge-Keane's  Technical  Methods,  vol. 
ii.  p.  231. 


CALORIMETERS  201 

Junkers  supplies  to  the  buyers  of  his  calorimeter  a  table 
for  estimating  the  heating  values  by  it. 

An  extensive  study  of  the  Junkers  calorimeter  has  been 
made  by  Immenkotter  in  his  booklet  "  Ueber  Heizwert- 
bestimmungew  mit  besonderer  Beriicksichtigung  gasfomiger 
Breunstoffe,"  published  by  Oldenbourg,  Munich,  an  abstract 
of  which  is  given  in/.  Gasbeleucht.,  1905,  p.  736. 

Junkers  has  also  modified  his  calorimeter  so  as  to  become 
an  automatically  registering  apparatus  (Ger.  Ps.  174753  an<^ 
190827 ;  /.  Gasbeleucht.,  1907,  p.  520).  He  effects  this  by 
keeping  the  relation  between  the  quantities  of  gas  and  water 
constant,  so  that  the  difference  of  temperature  is  a  direct 
measure  of  the  heating  value,  being  proportional  to  it.  The 
difference  of  temperature  between  the  inflowing  and  outflowing 
water  is  measured  by  a  thermo-element,  and  the  indications  of 
the  voltmeter  showing  the  tension  are  continuously  registered 
on  a  strip.  A  registering  gas-calorimeter  is  also  described  by 
Fahrenheim  (/.  Gasbeleucht.,  1907,  p.  1019). 

Coste  and  James  (/.  Soc.  Chem.  Ind.,  1911,  p.  67)  object  to 
the  Junkers  gas-calorimeter  that  the  water  used  in  it  may  be 
heated  by  the  air  of  the  room.  To  avoid  this,  they  correct 
the  test  by  a  blind  test,  or  they  preheat  the  water  to  the 
temperature  of  the  laboratory. 

Biicher  (Z.  Verein.  deutsch.  Ingen.,  1911,  p.  ino)  found  in 
the  exit  gases  some  unburnt  methane,  causing  a  loss  of  i  or  2 
per  cent,  of  the  heating  value.  In  spite  of  this  he  considers 
the  Junkers  calorimeter  as  a  sufficiently  correct  instrument  for 
practical  purposes. 

Allner  (Gas  Age,  xxxii.  p.  IS;/.  Gasbeleucht.,  1913,  Ivi. 
p.  489)  describes  a  contrivance  for  starting  an  alarm  bell  in 
case  of  a  sudden  stoppage  of  the  gas  or  water  supply  in  the 
registering-calorimeter  of  Junkers. 

(b)  Boys'  Gas-Calorimeter  (Proc.  Roy.  Soc.,  1906,  series  A, 
p.  122.  The  apparatus  is  made  by  J.  J.  Griffin  &  Sons,  Kings- 
way,  London). — This  apparatus  is  prescribed  by  the  Metro- 
politan Gas  Referees  (1906)  for  testing  the  calorific  value  of 
illuminating  gas.  It  has  been  designed  with  the  object  of 
providing  ample  space  for  the  circulation  of  the  stream  of  gases, 
so  that  they  pass  slowly  and  freely  through  the  instrument,  and 
are  thus  effectively  exposed  to  the  cooling  surfaces.  The  water 


202  TECHNICAL  GAS-ANALYSIS 

content  of  the  instrument  is  reduced  to  the  smallest  quantity, 
so  that  the  outflowing  water  attains  its  ultimate  temperature 
very  quickly  after  the  gas  is  lighted.  The  whole  of  the  circulat- 
ing water  takes  the  same  course  continously,  being  debarred 
from  any  parallel  or  alternative  routes,  and  thus  unequal 
heating  and  the  attendant  irregularity  of  the  temperature  at 
the  outflow  are  avoided.  The  small  content  of  water  suffices  to 
abstract  the  whole  of  the  heat  from  the  slowly  travelling  stream 
of  gases,  owing  partly  to  the  avoidance  of  parallel  routes,  but 
mainly  by  reason  of  its  flow  through  a  pipe  of  small  diameter, 
the  heat-collecting  power  of  which  is  greatly  increased  by 
attached  wires. 

This  calorimeter  is  shown  in  vertical  section,  one-half  natural 
size,  in  Fig.  go.  It  consists  of  three  parts  which  may  be 
separated,  or  which,  if  in  position,  may  be  turned  relatively  to 
one  another  about  their  common  axis.  The  parts  are  (i)  the 
base  R,  carrying  a  pair  of  burners  B,  and  a  regulating  tap. 
The  upper  surface  of  the  base  is  covered  with  a  bright  metal 
plate,  held  in  place  by  three  centring  and  lifting  blocks  C. 
The  blocks  are  so  placed  as  to  carry  (2)  the  vessel  D,  which  is 
provided  with  a  central  copper  chimney  E,  and  a  condensed 
water  outlet  F.  Resting  upon  the  vessel  D  are  (3)  the  essential 
parts  of  the  calorimeter,  attached  to  the  lid  G.  At  the  centre 
where  the  outflow  is  situated  there  is  a  brass  box,  which  acts  as 
a  temperature-equalising  chamber  for  the  outlet  water.  Two 
dished  plates  of  thin  brass,  K,  are  held  in  place  by  three  scrolls 
of  thin  brass,  L  L  L.  The  lower  or  pendent  part  of  the  box  is 
kept  cool  by  water,  circulating  through  a  tube  which  is  sweated 
on  to  the  outside  of  the  bell.  Connected  to  the  water-channel 
at  the  lowest  point  by  a  union,  are  six  turns  of  copper  pipe, 
such  as  is  used  in  a  motor-car  radiator  of  the  kind  known  as 
Clarkson's.  In  this,  a  helix  of  copper  wire  threaded  with 
copper  wire  is  wound  round  the  tube,  and  the  whole  is  sweated 
together  by  immersion  in  a  bath  of  melted  solder.  A  second 
coil  of  pipe  of  similar  construction,  surrounding  the  first,  is 
fastened  to  it  at  the  lower  end  by  a  union.  This  terminates  at  the 
upper  end  in  a  block,  to  which  the  inlet  water-box  and  thermo- 
meter-holder are  secured  by  a  union,  as  shown  at  O.  An 
outlet  water-box  P  and  thermometer-holder  are  similarly 
secured  above  the  equalising  chamber.  The  lowest  turns  of  the 


FIG.  90. 


204  TECHNICAL  GAS-ANALYSIS 

two  coils  N  are  immersed  in  the  water,  which  in  the  first  instance 
is  put  into  the  vessel  D. 

Between  the  outer  and  inner  coils  N  is  placed  a  brattice  O, 
made  of  thin  sheet  brass,  containing  cork  dust,  to  act  as  a  heat 
insulator.  The  upper  annular  space  in  the  brattice  is  closed  by 
a  wooden  ring,  and  this  end  is  immersed  in  melted  rosin  and 
bees-wax  cement,  to  protect  it  from  any  moisture  which  might 
condense  upon  it.  The  brattice  is  carried  by  an  internal  flange, 
which  rests  upon  the  lower  edge  of  the  casting  H.  A  cylindrical 
wall  of  thin  sheet  brass,  a  very  little  smaller  than  the  vessel  D, 
is  secured  to  the  lid,  so  that  when  the  instrument  is  lifted  out 
of  the  vessel  and  placed  upon  the  table,  the  coils  are  protected 
from  injury.  The  narrow  air  space  between  this  and  the  vessel 
D  also  serves  to  prevent  interchange  of  heat  between  the  calori- 
meter and  the  air  of  the  room. 

The  two  thermometers  for  reading  the  water  temperatures, 
and  a  third  for  reading  the  temperature  of  the  outlet  air,  are  all 
near  together,  and  at  the  same  level.  The  lid  may  be  turned 
round  into  any  position,  relatively  to  the  gas  inlet  and  the 
condensed  water  drip,  that  may  be  convenient  for  observation, 
and  the  inlet  and  outlet  water-boxes  may  themselves  be  turned 
so  that  their  branch  tubes  point  in  any  direction. 

The  general  arrangement  of  the  apparatus,  as  set  up  for  a 
test,  is  shown  in  Fig.  91,  the  gas  being  first  passed  through  a 
meter  and  balance  governor  before  being  led  to  the  calorimeter. 
The  gas  supply  is  connected  up  to  the  central  tube  at  the  back 
of  the  meter  and  thence  to  the  governor,  preferably  by  means 
of  composition  piping.  The  pipe  leading  from  the  governor 
should  terminate  in  a  nozzle,  to  which  a  short  length  of  rubber 
tubing  is  attached  for  connecting  to  the  calorimeter. 

A  regular  supply  of  water  is  maintained  by  connecting  one 
of  the  two  outer  pipes  of  the  overflow  funnel,  shown  in  Fig.  91, 
to  a  small  tap  over  a  sink.  The  overflow  funnel  is  fastened  to 
the  wall  about  i  meter  above  the  sink,  and  the  other  outer 
pipe  is  connected  to  a  tube,  in  which  there  is  a  diaphragm  with 
a  hole  2-3  mm.  in  diameter.  This  tube  is  connected  to  the 
inlet-pipe  of  the  calorimeter.  A  piece  of  stiff  rubber  tubing, 
long  enough  to  carry  the  overflow  water  clear  of  the  calorimeter, 
is  slipped  on  to  the  outflow  branch,  and  the  water  is  turned  on 
so  that  a  little  of  it  escapes  by  the  middle  pipe  of  the  overflow 


206  TECHNICAL  GAS-ANALYSIS 

funnel,  and  is  led  by  a  third  piece  of  tube  into  the  sink.  The 
amount  of  water  that  passes  through  the  calorimeter  in  four 
minutes  should  be  sufficient  to  fill  the  graduated  vessel,  shown 
in  Fig.  91,  to  some  point  above  the  lowest  division,  but  insufficient 
to  come  above  the  highest  division  in  five  minutes.  If  this  is 
not  found  to  be  the  case,  a  moderate  lowering  of  the  overflow 
funnel  or  reaming  out  of  the  hole  in  the  diaphragm  will  effect 
the  necessary  connection. 

The  thermometers  for  reading  the  temperature  of  the  inlet 
and  outlet  water  are  divided  into  tenths  of  a  degree,  and  are 
provided  with  reading-lenses  and  pointers  sliding  upon  them. 
The  thermometers  are  held  in  place  by  corks,  fitting  the  inlet 
and  outlet  water-boxes.  The  thermometers  for  reading  the 
temperature  of  the  air  near  the  instrument  and  of  the  outlet 
gases  are  divided  into  degrees. 

The  flow  of  air  to  the  burners  is  determined  by  the  degree  to 
which  the  passage  is  restricted  at  the  inlet  and  at  the  outlet. 
The  blocks  C  (Fig.  91)  which  determine  the  restriction  of  the 
inlet  are  made  of  metal,  about  5  mm.  thick,  while  the  holes 
round  the  lid  which  determine  the  restriction  at  the  outlet 
are  five  in  number  and  are  16  mm.  in  diameter.  The 
thermometer  used  for  finding  the  temperature  of  the  effluent 
gas  is  held  by  a  cork  in  the  sixth  hole  of  the  lid,  so  that  the 
bulb  is  just  above  the  upper  coil  of  the  pipe. 

The  calorimeter  should  stand  on  a  table  by  the  side  of 
a  sink,  so  that  the  condensed  water  and  hot-water  outlets 
overhang  and  deliver  into  the  sink,  as  shown  in  Fig.  91.  A 
glass  vessel  is  provided  of  the  size  of  the  vessel  D,  which 
should  be  filled  with  water,  in  which  sufficient  carbonate  of 
soda  is  dissolved  to  make  it  definitely  alkaline.  The  calori- 
meter, when  not  in  use,  is  lifted  out  of  the  vessel  D  and  placed 
in  the  alkaline  solution,  and  left  there  until  it  is  again  required. 
The  liquid  should  not  come  within  2  in.  of  the  top  of  the  vessel, 
when  the  calorimeter  is  placed  in  it.  The  liquid  must  be 
replenished  from  time  to  time,  and  its  alkalinity  maintained. 

The  measuring  vessel,  shown  in  Fig.  91,  carries  a  change- 
over funnel,  which  is  placed  beneath  the  short  tube  attached 
to  the  hot-water  outlet.  One  side  of  the  funnel  delivers  into 
the  sink,  and  the  other  delivers  into  a  tube,  which  directs  the 
water  into  the  vessel. 


CALORIMETERS 


207 


Full  details  for  carrying  out  a  test  are  given  in  the 
Modification  of  the  Metropolitan  Gas  Referees  for  1906 
(published  by  Wyman  &  Sons,  Fetter  Lane,  London,  E.G., 
price  is.  6d.) ;  the  above  description  is  taken  from  this 
notification. 

Boys'  calorimeter  has  these  advantages  over  Junkers',  that 
the  thermometers  for  the  entering  and  the  exit  water  are  at 
the  same  level,  that  the  apparatus  can  be  taken  to  pieces  in 
a  few  minutes,  and  that  the  water  contents  are  reduced  from 
about  1700  to  about  300  c.c. 

(c)  F.  Fischer's  Gas- Calorimeter  (Fig.  92)  consists  of  a 
wooden  vessel  B,  in  which  nickel- 
plated  copper  vessels  A  and  C 
are  contained.  A  is  suspended 
from  the  top  of  B  as  shown,  and 
C  is  fitted  into  B  by  the  water- 
tight junction  at  v,  which  should 
be  greased  before  use.  The  de- 
tachable cover  D  is  provided  with 
an  attachment  at  t  for  inserting 
a  thermometer,  and  to  carry  the 
stirrer  R.  The  inner  vessel  C 
is  expanded  into  three  lenticular 
chambers,  each  of  which  contains 
a  sheet  of  metal  «,  serrated  round 
the  edge,  the  object  of  which  is  F 
to  promote  intimate  contact  be- 
tween the  products  of  combustion 
and  the  inner  surface  of  the 
colorimeter.  The  whole  vessel  is 
supported  on  the  feet  F.  The 
burner  E  is  supported  by  the 
socket  f  and  the  arm  m>  and  is 
so  arranged  that  it  can  be  readily  adjusted  into  position,  by 
means  of  the  tongue  a  and  a  pin  below  f.  A  small  inverted 
cone  of  nickel  gauze  is  placed  in  the  tube  of  the  burner,  to 
prevent  the  gas  from  striking  back.  Even  very  small  flames 
burn  very  quietly  here.  A  cone,  preferably  of  platinum  gauze, 
with  the  apex  upwards,  may  also  be  fitted  to  the  top  of  the 
burner  tube.  Air  enters  at  the  inclined  plate  s,  the  direction 


FIG.  92. 


208  TECHNICAL  GAS-ANALYSIS 

of  which  serves  to  retain  the  condensed  water  in  the  calori- 
meter, and  the  waste  gases  leave  through  b. 

To  carry  out  a  determination,  the  required  quantity 
of  water  is  placed  in  A,  the  inner  vessel  C  is  placed  in 
position,  the  cover  D  put  on,  and  a  thermometer  inserted  at 
t.  The  water  is  agitated  by  the  stirrer  until  the  temperature 
is  constant,  and  the  burner  drawn  down  below  the  body  of 
the  calorimeter  and  attached  to  the  gas  supply  ;  the  gas 
should  be  passed  through  the  meter  for  some  time  previous 
to  the  determination,  in  order  to  saturate  the  contained  water. 
The  burner  is  then  lighted  and  quickly  introduced  into  the 
position  shown  ;  the  flame  is  adjusted  for  complete  combustion, 
that  adjustment  being  best  determined  by  a  preliminary  experi- 
ment, so  as  to  ensure  an  excess  of  5  per  cent,  oxygen  in  the 
waste  gases.  In  testing  semi-water  gas  or  producer-gas,  the 
air  holes  at  the  bottom  of  the  burner  are  closed  ;  in  the  case 
of  difficultly  combustible  gases,  such  as  blast-furnace  gas,  it 
is  recommended  to  supply  oxygen  (about  one-fifth  of  the 
volume  of  the  gas)  through  a  tube  fixed  in  the  centre  of  the 
burner.  The  state  of  the  meter  is  read  off;  then  exactly  at  the 
same  moment  burner  B  is  moved  by  the  right  hand  beneath  the 
calorimeter  until  m  touches  ny  and  burner  E  is  placed  in  the 
position  shown  in  the  drawing,  which  takes  hardly  one  second. 
When  the  requisite  volume  of  gas  (say,  I  litre  of  coal-gas,  ij  to 
2  litres  of  water-gas,  and  3  litres  of  producer-gas  or  semi-water 
gas)  has  been  burned,  the  rubber  tube  connected  with  E  is 
closed  by  pressing,  and  the  temperature  of  the  water  in  the 
calorimeter  read,  after  agitating  with  the  stirrer  for  two 
minutes. 

The  increase  of  temperature,  multiplied  by  the  heat 
equivalent  of  the  calorimeter,  gives  the  calorific  value  of 
the  total  gas  burnt,  which  can  be  calculated  to  the  gross  value 
per  cubic  metre  at  normal  pressure  and  15°,  as  described 
above.  This  is  quite  sufficient  for  checking  the  work,  and 
such  a  determination  can  be  made  in  a  few  minutes.  To 
obtain  the  net  value,  in  the  first  instance  the  volume  read  off 
in  the  meter  must  be  reduced  to  normal  pressure  and  o°  by 
the  well-known  formula  : 


760 


CALORIMETERS  209 

the  gas  in  the  meter  being  completely  saturated  with  water; 
e.g.,  1000  c.c.  gas  measured  at  20°  and  747  mm. 

=  'OOP  x  (747 -17)    =  896  c.c. 
760  x  (1  +  0-0732) 

When  neglecting  this  reduction  errors  of  10  per  cent,  are  easily 
made. 

Most  of  the  water  formed  in  the  combustion  collects  in 
C  and  is  weighed  in  this  vessel,  by  first  emptying  the  water 
out  of  A,  and  then  detaching  and  weighing  C,  after  carefully 
drying  it  outside,  the  weight  of  the  empty  vessel  having  been 
previously  ascertained.  For  each  10  mg.  water,  6  cal.  are 
deducted,  if,  as  usual,  the  calorific  value  is  determined  for 
steam  of  20°.  C  is  then  washed  with  distilled  water  (to 
remove  SO2  and  H2SO4)  and  dried,  to  be  ready  for  the 
next  test. 

(d)  Various  Gas- Calorimeters. — Graefe  (Z.  fiir  chem.  Appara- 
tenkunde,  1906,  pp.  320  and  723  ;  cf.  also  Pleyer,/.  Gasbeleucht., 
19°7>  P-  83  0  employs  a  nickel-coated  brass  cylinder,  containing 
wire  nets  against  which  the  combustion  gases  strike  and  to  which 
they  yield  up  their  heat.  Each  instrument  must  be  gauged 
with  a  Junckers'  calorimeter,  as  part  of  the  gases  escapes  with 
a  higher  temperature.  The  gas  comes  from  a  measuring  bottle 
with  constant  overflow,  and  is  burnt  by  a  tuyere  into  a  flame  of 
2  or  3  cm.  height. 

Hempel  (Z.  angew.  Chem.^  1901,  p.  713)  describes  a  calori- 
meter for  small  quantities  (2  or  3  litres)  of  gas,  and  another 
calorimeter  in  Gasanal.  Methoden,  4th  ed.,  pp.  383  et  seq. 

Raupp's  gas-calorimeter  (as  reported  by  Lux  in  J.  Gas- 
beleucht.,  1906,  p.  475)  contains  a  copper  cylinder,  the  lower 
part  of  which  is  solid,  the  upper  part  containing  a  thermometer 
divided  in  tenths  of  a  degree.  Below  the  cylinder  at  an  exactly 
measured  moment  a  gas-flame  of  previously  ascertained  height 
is  placed,  and  by  means  of  a  watch  the  time  is  noted  which  is 
required  to  raise  the  temperature  of  the  thermometer  by  10°. 

Stoecker  and  Rothenbach  (J.  Gasbeleucht.,  1908,  p.  121) 
describe  a  simple  gas-calorimeter  for  small  quantities  of  gas, 
but  Mayer  and  Schmiedt  (ibid.,  p.  1164)  find  fault  with  the 
exactness  of  the  results  obtained  thereby. 

The   Simmance-Abady   calorimeter   (B.  P.  27920  of   1912, 

O 


210  TECHNICAL  GAS-ANALYSIS 

made  by  A.  Wright  &  Co.,  Westminster)  resembles  the  Junckers 
instrument,  but  the  gases  travel  downwards  through  a  series  of 
annular  chambers,  separated  by  similar  chambers  up  which  the 
water  flows.  Both  thermometers  of  this  instrument  are  at  the 
same  level,  and  by  their  side  is  a  manometer  tube  to  slow  the 
pressure  of  the  inlet  water  which  must  be  kept  constant ; 
a  damper  is  provided  at  the  waste-gas  exit,  for  the  regulation 
of  the  volume  of  the  air  passing  through  the  apparatus,  and  the 
condensed  water  flows  through  a  small  exit  drain  into  a 
measuring  cylinder. 

Coste  and  James  describe  a  new  calorimeter  which  can  be 
worked  with  very  small  volumes  of  gas  (J.  Soc.  Chem.  Ind.y 

191 1,  p.  258). 

Parr  (Progressive  Age,  1911,  p.  1059;  Z.  angew.  Chem.^  1912, 
p.  1420)  burns  both  hydrogen  and  the  gas  to  be  tested  at  the 
same  time  and  in  altogether  similar  apparatus,  and  computes 
the  calorimetric  value  of  the  second  gas  by  comparing  it  with 
that  of  the  hydrogen. 

Strache's  gas-calorimeter  consists  of  an  explosion  pipette, 
surrounded  by  an  air-jacket,  the  expansion  of  which  is  read  off 
by  a  pressure  gauge  and  directly  indicates  the  heating  value  of 
the  gas.  Certain  drawbacks  of  the  original  apparatus  are 
avoided  in  a  modification  constructed  by  Breysig  (/.  Gasbeleucht., 

1912,  Iv.  p.  833). 

A  new  apparatus  for  estimating  the  heating  value  of  gases, 
called  Sarco-calorimeter,  is  described  in  J.  Gasbeleucht.^  1913, 
p.  381.  It  consists  of  a  U-tube  filled  with  oil,  one  of  the  limbs 
being  at  the  temperature  of  the  surrounding  air,  the  other  limb 
being  heated  by  the  combustion  of  the  gas. 

Other  gas-calorimeters  have  been  described  by  Smith 
(/.  Gas  Lighting,  cxx.  p.  1051);  Macklow,  Smith,  and  Pullen 
(B.  P.  1905,  of  1911). 

Weyman  (/.  Soc.  Chem.  Ind.y  1914,  p.  11)  discusses  the 
difference  between  the  calculated  and  determined  calorific 
values  of  coal-gas. 

X.  DETERMINATION  OF  THE  ILLUMINATING  POWER 
OF  GASES. 

This  operation,  which,  of  course,  is  only  carried  out  with 
coal-gas  or  other  gases  used  for  illuminating  purposes,  does  not 


OXYGEN  211 

belong  to  the  domain  of  technical  gas-analysis.  We  shall 
therefore  only  state  that  it  is  carried  out  by  means  of 
photometers,  by  comparing  the  flame  to  be  tested  with  a 
standard  light,  usually  the  pentane  lamp,  the  Hefner  amylacetate 
lamp,  or  the  carbon-filament  incandescent  lamp. 

Very  many  photometers  have  been  devised,  of  which  that 
designed  by  Bunsen  is  most  widely  used.  For  a  detailed 
treatment  of  this  subject  we  refer  to  the  chapter  on  gas- 
manufacture  by  Pfeififer,  in  Lunge  and  Berl's  Chemisch-technische 
Untersuchungsmethoden,  vol.  iii.  pp.  320  et  seq.  (1911);  English 
translation  by  Keane,  vol.  ii.  pp.  697  et  seq. 


SPECIAL  METHODS  FOR  DETECTING  AND  ESTI- 
MATING VARIOUS  GASES  OCCURRING  IN 
TECHNICAL  OPERATIONS. 

OXYGEN. 

The  estimation  of  oxygen  has  been  described  in  a  number 
of  places  in  the  preceding  chapters,  especially  pp.  119  et  seq. 

We  shall  now  describe  some  special  apparatus  and  methods 
for  this  purpose. 

Lindemanrfs  apparatus  is  shown  in  Fig.  93.  The  measuring- 
tube  A  has  a  three-way  cock  at  the  top,  but  no  tap  at  the 
bottom.  It  contains  altogether  100  c.c.,  75  c.c.  of  this  in  the 
globular  and  25  c.c.  in  the  cylindrical  part,  which  is  divided  into 
tenths  of  a  cubic  centimetre.  The  levelling  bottle  C  contains  water, 
the  absorbing  vessel  B  thin  sticks  of  phosphorus  and  water  up 
to  the  mark.  The  gas  is  introduced  through  the  pinchcock 
arrangement  connected  with  the  three-way  cock  ;  otherwise  the 
manipulation  is  exactly  as  with  the  Orsat  apparatus  (p.  66). 

This  apparatus  serves  for  the  rapid  estimation  of  oxygen  in 
air,  both  ordinary  and  that  from  graves,  respiration,  Weldon's 
oxydisers,  Bessemer  converters,  vitriol  chambers,  etc.,  especially 
also  in  the  waste  gases  from  sulphuric  acid  chambers,  from  the 
Deacon  process,  etc. 

Method  of  Pfeiffer  (J.  Gasbeleucht.,  1897,  p.  354).  This  is 
specially  intended  for  estimating  the  small  quantities  of  oxygen 
occurring  in  coal-gas.  This  slight  proportion  of  oxygen  has 


212 


TECHNICAL  GAS-ANALYSIS 


no  sensible  influence  on  its  quality,  but  it  should  be  ascertained 
with  reference  to  the  manufacture  of  the  gas,  since  it  has 
become  quite  general  to  mix  I  or  2  vols.  per  cent,  oxygen  with 
crude  gas  before  purification,  in  order  to  bring  about  a  partial 
regeneration  of  the  purifying  mass  already  in  the  boxes.  The 
regenerating  air  is  introduced  into  the  crude  gas  by  a  branch 


FIG.  93. 

pipe  of  the  gas  tubing  in  front  of  the  aspirator ;  the  air  thus 
introduced  is  measured  from  time  to  time  by  means  of  an 
interposed  meter,  and  the  velocity  of  the  air-current  regulated 
accordingly.  Of  course  it  is  unavoidable  that  somewhat  great 
varieties  occur  in  the  admixture  of  air  with  the  gas,  as  this 
depends  on  the  action  of  the  aspirator  and  the  partial  vacuum 
produced  by  this. 

Such  small  percentages  of  oxygen,  according  to  Pfeiffer, 
can  be  estimated  colorimetrically  by  the  formation  of  strongly 
colouring  matters,  taking  place  when  a  caustic  solution  is 
brought  into  contact  with  pyrogallol  in  the  presence  of  oxygen, 
which  can  be  easily  done  in  a  Bunte  burette.  One  hundred 


OXYGEN  213 

c.c.  of  gas  is  introduced  into  the  burette  and  measured  in  the 
way  above  described  (p.  61).  The  water  is  now  drawn  off 
from  the  bottom  of  the  burette  and  replaced  by  5  c.c.  caustic 
potash  solution  (i  :  2).  The  height  occupied  by  this  quantity 
of  liquid  is  marked  once  for  all  on  the  burette  by  a  slight 
file-stroke.  The  funnel  above  ought  at  first  to  contain  water 
only  in  the  capillary.  Into  this  funnel  02  g.  pyrogallol  is  put 
and  covered  with  2  c.c.  water,  which  dissolves  it.  The  solution 
is  drawn  into  the  burette,  leaving  a  drop  behind  which  closes 
the  capillary.  The  oxygen  in  the  burette  is  absorbed  by 
shaking  for  two  minutes.  Now  from  below  a  sufficient 
quantity  of  water,  free  from  oxygen  (see  below),  is  allowed 
to  enter,  until  a  certain  mark,  say  o,  has  been  reached.  Two 
minutes  after  finishing  the  agitation,  the  colour  produced  is 
compared  with  that  shown  in  a  wide  test-tube,  containing  10 
c.c.  of  water,  into  which  decinormal  iodine  solution  is  run  drop 
by  drop  from  a  burette,  until  the  colours  are  identical.  The 
observation  is  best  made  by  holding  both  tubes  with  one  hand 
against  the  light,  putting  the  other  hand  across  them  and 
leaving  only  a  gap  between  the  fingers  for  looking  through. 
The  number  of  drops  required  corresponds  to  a  certain 
percentage  of  air,  empirically  produced  as  below,  which  can 
be  read  off  directly  from  a  small  table. 

The  decinormal  iodine  solution  employed  for  comparison 
contains  2  parts  potassium  iodide  to  I  part  free  iodine;  in 
dilute  solutions  the  colour  is  exactly  like  that  of  the  galloflavine, 
produced  from  the  pyrogallol.  In  order  to  establish  the  "  titre  " 
of  this  iodine  solution,  artificial  mixtures,  containing  J,  I,  2,  3 
per  cent,  of  air  are  treated  in  the  Bunte  burette  with  alkaline 
pyrogallol  in  the  above-described  way.  When  the  burette  has 
been  filled  with  water  up  to  the  zero  mark,  10  c.c.  of  water  is 
put  into  the  test-tube  intended  for  receiving  the  comparing 
liquid,  and  from  a  small  tube  so  much  iodine  solution  is  added, 
drop  by  drop,  that  the  liquid  shows  exactly  the  same  colour 
as  that  in  the  burette.  The  eye  permits  easily  to  distinguish 
the  difference  of  colour  produced  by  a  single  drop.  The 
observation  is  always  made  two  minutes  after  finishing  the 
agitation.  For  instance  the  following  number  of  drops  was 
required  for  various  contents  of  air:  0-5  per  cent,  air  =4  drops; 
I  per  cent,  air  =11  drops;  2  per  cent,  air  =33  drops;  3  per 


214  TECHNICAL  GAS-ANALYSIS 

cent,  air  =  66  drops.  These  are  average  values  from  a  number 
of  tests,  the  outside  limits  of  which  at  the  worst  would  cause 
an  error  of  J  per  cent,  air  (  =  0-05  per  cent,  oxygen).  It  is 
recommended  to  enter  the  values  found  on  "  millimetre  paper  " 
in  a  curve,  the  air  percentages  as  abscisses,  and  the  number  of 
drops  as  ordinates,  in  order  to  save  the  trouble  of  making 
interpolations.  The  values  found  for  air  are  converted  into 
percentages  of  oxygen  by  multiplying  them  with  0-21. 

The  mixtures  of  gas  and  air  required  for  this  comparison 
are  best  produced  in  the  burette  itself.  About  100  c.c.  of  gas 
is  in  the  first  place  treated  for  the  removal  of  oxygen  by  any 
of  the  well-known  methods.  Then  the  quantities  of  air:  0-5, 
I,  2,  or  3  c.c.,  are  measured  off  by  means  of  a  pipette,  divided 
from  the  point  upwards,  by  connecting  its  bottom  end  with 
the  rubber  tube  of  the  small  water  reservoir  belonging  to  the 
Bunte  burette.  The  water  is  allowed  to  rise  up  to  the  desired 
mark  in  the  pipette,  the  point  is  put  into  the  short  rubber  tube 
usually  placed  over  the  lateral  opening  of  the  three-way  cock, 
this  cock  is  turned  180°,  and  the  air  is  driven  from  the  tube 
into  the  burette  by  means  of  water  run  in  at  the  top.  Then 
the  cock  is  turned  back  again. 

The  air  contained  in  the  water  used  for  filling  the  burette 
up  to  the  zero  mark  may  amount  up  to  o  I  c.c.  oxygen.  This 
is  but  a  small  quantity,  and  it  is  probably  always  much  the 
same ;  it  can  be  neglected,  since  always  the  same  quantity  of 
water  is  employed.  If  you  wish  to  be  entirely  independent 
of  this  constant,  especially  in  order  to  get  a  sharper  result  for 
qualitative  tests,  you  must  prepare  for  these  tests  water  free 
from  oxygen.  Pfeiffer  obtains  this  by  contact  with  zinc,  made 
specially  active  by  covering  it  with  water  containing  I  or  2 
drops  of  cupric  sulphate  solution,  pouring  off  the  liquid  after 
a  quarter  of  an  hour,  and  washing  with  water.  Granulated  zinc 
treated  in  this  manner  is  put  into  a  J-litre  Woulff's  bottle. 
Through  one  of  the  necks  of  this  bottle,  a,  a  tube  goes  down  to 
the  bottom,  closed  there  by  a  plug  of  cotton-wool,  in  order  to 
retain  any  flakes  of  zinc  oxide ;  the  upper  end  carries  a  rubber 
tube  about  10  cm.  long,  with  pinchcock.  The  second  neck  is 
closed  by  a  doubly  perforated  stopper,  through  which  pass  two 
short  tubes,  b  and  c.  Tube  b  projects  a  little  into  the  bottle ;  tube 
c  ends  below  flush  with  the  stopper,  and  at  the  top  is  closed  by 


OXYGEN  215 

a  short  rubber  tube,  closed  by  a  glass  rod.  The  bottle  is  filled 
with  water,  and  this  is  saturated  with  coal-gas  (tube  a  being 
connected  with  the  gas  pipe,  tube  b  with  an  aspirator).  By 
jerking  the  bottle  against  the  palm  of  the  hand,  any  air  or  gas 
bubbles  between  the  bits  of  zinc  are  removed.  Now  connect 
tube  b  with  the  rubber  tube  of  the  air  reservoir  belonging  to 
the  Bunte  burette,  and  thus  place  the  bottle  under  pressure. 
By  lifting  the  stopper  c  allow  the  gases,  collected  at  the  top, 
to  escape.  After  a  few  hours  the  water  in  the  bottle  will  be 
free  from  oxygen,  which  is  tested  for  by  making  a  sample  of 
it  alkaline  and  adding  a  drop  of  manganous  chloride  solution, 
which  should  produce  a  perfectly  white  precipitate  of  hydrated 
manganese  protoxide.  For  use  the  water  is  taken  out  of  tube 
a  by  allowing  it,  after  opening  the  pinchcock,  to  rise  into  the 
rubber  continuation  and  from  this  into  the  burette,  the  point 
of  which  has  been  connected  with  that  rubber  pipe.  The 
water  running  down  from  the  upper  reservoir  at  once  comes 
into  contact  with  the  zinc  ;  since  it  is  prevented  by  this  from 
moving  freely,  it  does  not,  when  gradually  used,  get  to  the 
bottom  of  the  bottle  until  it  has  yielded  up  all  its  oxygen  to 
the  zinc. 

Before  estimating  the  oxygen  in  crude  coal-gas,  first  the 
sulphuretted  hydrogen  must  be  removed  by  caustic  alkali,  as 
this  gas  in  the  presence  of  oxygen  imparts  to  the  pyrogallol 
solution  a  Burgundy-red  colour. 

Another  very  simple  method  has  been  worked  out  by 
Pfeiffer  (/.  Gasbeleucht.,  1898,  p.  605)  for  the  determination  of 
the  "  neutral  zone  "  of  combustion  in  the  flues  of  retort-furnaces 
(or  other  fireplaces),  t.e.t  the  point  at  which  free  oxygen  first 
appears  in  the  mixed  gases,  for  which  purpose  a  quantitative 
estimation  of  the  oxygen  is  unnecessary.  The  apparatus, 
shown  in  Fig.  94,  consists  of  a  calcium-chloride  tube,  about 
30  c.c.  long,  in  which  are  placed  a  few  thin  sticks  of  yellow 
phosphorus,  about  1 5  c.c.  long.  The  lower  end  is  closed  with 
a  cork  fitted  with  a  doubly-bent  glass  tube,  and  the  whole  is 
placed  in  a  jar  containing  sufficient  water  to  cover  the 
phosphorus  and  to  prevent  its  oxidation  by  the  air.  To  use 
the  apparatus,  the  tube  containing  the  phosphorus  is  lifted 
out  of  the  jar  and  the  water  allowed  to  drain  out;  the  bent 
glass  tube  is  then  connected  to  the  porcelain  tube  through 


216 


TECHNICAL  GAS-ANALYSIS 


which  the  sample  is  drawn  from  the  flues,  the  upper  end  to 
an  aspirator,  and  the  tube  is  then  replaced  in  the  water  to 
protect  it  from  the  heat  radiated  from  the  brickwork.  The 
temperature  of  the  water  must  not  be  below  15°,  as  phosphorus 
does  not  combine  with  oxygen  below  that  tem- 
perature. The  flues  are  then  tested  in  order 
from  top  to  bottom ;  as  soon  as  oxygen  is 
present  in  appreciable  quantity,  thick  white 
fumes  of  phosphorus  oxides  are  formed.  A 
slight  mist  is  formed  at  each  suction  of  the 
stroke  of  the  aspirator,  due  to  the  deposition 
of  moisture  owing  to  the  cooling  of  the  gas 
by  expansion ;  but  this  is  quite  distinct  in 
appearance  from  the  phosphorous  fumes,  and 
cannot  be  mistaken  for  them. 

Lubberger  (/.  Gasbeleucht.,  1898,  p.  695) 
employs  the  following  method  for  the  estima- 
tion of  oxygen :  bringing  the  gas  in  a  Bunte 
burette  into  contact  with  alkali  and  manganous 
hydrate,  whereby  manganic  hydrate  is  formed 
After  acidulating  with  hydrochloric  acid  and 
adding  potassium  iodide,  the  liberated  quantity  of  iodine,  which 
is  equivalent  to  the  oxygen  originally  present  in  the  gas,  can  be 
titrated  with  sodium  thiosulphate. 

The  following  liquids  are  required  for  this  process :  (a)  a 
solution  of  potassium  iodide  (10  g.  NaOH,  35  g.  potassium  sodium 
tartrate,  8-5  g.  KJ,  dissolved  in  300  c.c.  water);  (U)  manganese 
solution  (10  g.  MnCl2,  dissolved  in  100  c.c.  water);  (c)  centi- 
normal  thiosulphate  solution  (2-48  g.  Na2S2O3+5H2O,  dissolved 
in  I  litre) ;  (d)  water  free  from  oxygen,  prepared  by  the  process 
described  suprfr,  in  connection  with  Pfeiffer's  method.  The  gas, 
about  100  c.c.,  is  measured  in  the  burette.  The  water  is  drawn 
off  from  below,  and  3  c.c.  of  the  potassium-iodide  solution  is 
allowed  to  enter  into  the  burette  from  here,  as  well  as  i  c.c. 
of  the  manganese  solution  through  the  top  funnel.  The  whole 
is  vigorously  shaken  up  for  ten  minutes,  so  that  the  liquid  is 
jerked  all  over  the  inside  of  the  burette.  Now  I  c.c.  con- 
centrated hydrochloric  acid  is  allowed  to  enter  from  below, 
and  the  burette  agitated.  Any  oxygen  present  in  the  gas  is 
already  now  indicated  by  iodine  being  set  free  and  causing 


FIG.  94. 


OXYGEN  217 

a  yellow  coloration.  In  the  acid  liquid  no  more  iodine  is 
liberated  by  oxygen.  The  contents  of  the  burette  are  washed 
into  a  beaker  by  pouring  water  into  the  top  funnel,  starch 
solution  is  added,  and  the  titration  made  by  adding  centi- 
normal  thiosulphate  solution  until  the  blue  colour  has  been 
destroyed.  From  the  quantity  of  thiosulphate  used  0-3  c.c. 
must  be  deducted,  as  shown  by  experience.  Each  cubic  centi- 
metre of  thiosulphate  indicates  0-12  vol.  per  cent,  of  oxygen,  if 
100  c.c.  gas  has  been  operated  upon.  Here  also  the  H2S 
must  be  previously  removed.  (Pfeiffer  did  not  find  this 
method  to  give  satisfactory  results.) 

The  apparatus  and  method  of  Chlopin  (Arch.  f.  Hygiene , 
1900,  p.  323)  is  more  particularly  intended  for  hygienic 
purposes ;  it  is  described  in  Lunge-Keane's  Technical  Methods, 
vol.  i.,  pp.  867  et  seq.  James  Miller  (/.  Soc.  Chem.  Ind.,  1914,  p. 
185)  absorbs  the  oxygen  dissolved  in  water  by  ferrous  sulphate. 

Hale  and  Mella  (/.  Ind.  and  Engin.  Chem.,  1913,  p.  976) 
studied  the  influence  of  the  presence  of  nitrite  for  the  deter- 
mination of  oxygen  dissolved  in  water  by  L.  W.  Winkler's 
method  (p.  218).  They  found  this  method  to  be  very  easy, 
rapid,  and  accurate.  Nitrite  as  present  in  the  usual  run  of  waters 
has  no  appreciable  effect  upon  the  accuracy  of  the  results ; 
but  if  present  in  quantities  upward  of  02  per  metre  it  increases 
the  results  by  a  catalytic  reaction.  This  effect  may  be  counter- 
acted by  the  use  of  potassium  acetate  solution,  or  sodium 
acetate  crystals,  to  neutralise  the  hydrochloric  acid  before 
exposure  to  the  air. 

Reaction  of  Nitric  Oxide  with  Oxygen. — This  reaction  varies 
according  to  the  excess  of  one  or  the  other  of  these  gases, 
and  whether  moisture  is  present  or  not.  Already  Priestley 
and  Cavendish  tried  to  estimate  the  oxygen  in  atmospheric 
air  in  this  manner,  but  Berthelot  (Comptes  rend.,  Ixxvii.  p.  1448) 
and  Lunge  (Ber.,  1885,  p.  1376)  did  not  get  satisfactory  results 
thereby.  The  better  results  of  Wanklyn  and  Cooper  (Chem. 
News,  Ixii.,  pp.  155  and  179)  have  been  proved  to  be  unreliable 
by  de  Coninck  (Z.  angew.  Chem.,  1891,  p.  78).  According  to 
Klinger  (Ber.,  1913,  p.  1745)  oxygen  can  be  correctly  examined 
by  employing  an  excess  of  nitric  oxide,  by  strictly  keeping 
out  moisture  from  the  gases,  and  especially  by  employing 
perfectly  dry  sticks  of  caustic  potash  for  absorbing  the 


218  TECHNICAL  GAS-ANALYSIS 

nitrogen  trioxide  formed  by  the  reaction  :  4NO-fO2  =  2N2OS, 
in  which  case  one-fifth  of  the  contraction  observed  after  the 
treatment  with  KOH  is  due  to  the  oxygen. 

Calafat  y  Leon  (B.  P.  4141  of  1913;  Ger.  P.  267493; 
Z.  angew.  Chem.y  1914,  ii.  p.  9)  makes  use  of  the  fact  that 
the  temperature  of  a  flame  is  dependent  on  the  proportion 
of  oxygen  in  the  air  supporting  combustion.  A  thermometer 
of  special  form  is  employed,  the  bulb  being  surrounded  by 
spongy  platinum  wires,  which  act  as  the  burner.  The  air  is 
passed  over  wool  and  pumice  saturated  with  methyl  alcohol, 
and  combustion  commences  when  it  comes  in  contact  with 
the  spongy  platinum. 

Leon  (Fr.  P.  454109)  also  estimates  the  oxygen  in  air  by 
saturating  this  with  methyl  alcohol,  and  passing  the  mixture 
through  a  platinum  sponge  lamp  which  influences  a  pyrometer, 
the  indication  of  which  is  dependent  on  the  degree  of  energy 
of  the  combustion. 

Binder  and  Weinland  (Berl.  Ber.,  1913,  p.  255)  discover  and 
estimate  free  oxygen  by  the  deep  red  colour  produced  in  an 
alkaline  solution  of  pyrocatechine  and  ferrous  sulphate,  through 
the  formation  of  tri-pyrocatechine-ferri-acid :  [Fe(C6H4O2)3]H3. 
They  carry  this  out  in  a  glass  cylinder,  through  the  cork  of 
which  passes  the  gas-pipe  and  a  drop-funnel ;  a  little  below 
the  cork  a  side-tube  branches  off,  connected  with  a  glass  valve. 
The  dry  cylinder  is  charged  with  0-4  g.  pure  Mohr's  salt,  free 
from  ferric  peroxide,  and  0-5  g.  pyrocatechine.  The  funnel  is 
filled  with  boiled  water,  and  pure  hydrogen,  freed  from  any 
oxygen  by  passing  it  through  alkaline  sodium  hydrosulphite 
solution,  is  passed  through.  In  any  case  a  slight  red  colour  is 
produced,  but  a  strong  colour  ensues  if  the  gas  to  be  tested 
contains  any  oxygen.  The  formation  of  the  above-mentioned 
compound  may  also  be  used  for  a  quantitative  estimation  of 
the  oxygen  present  in  the  gas  by  means  of  a  Hempel  pipette 
which  must  be  vigorously  shaken  for  five  minutes. 

L.  W.  Winkler  (Z.  angew.  Ckem.,  191 1,  pp.  341  and  831  ;  1913, 
p.  134)  estimates  oxygen  dissolved  in  water,  approximately  by  a 
mixture  of  "  adurol "  with  the  ammoniacal  solution  of  ammonium 
bromide,  or  with  borax,  which  produce  a  deep  red  colour. 

Haldane's  apparatus  is  based  on  the  observation  that  a 
candle  flame  is  extinguished  with  a  certain  dilution  of  the 


OZONE  219 

oxygen  ;  it  is  contended  by  Schorrig  (Abstr.  Amer.  Chem. 
Soc.,  1913,  vii.  p.  1993)  that  this  gives  a  better  idea  as  to 
the  suitability  of  mine  air  for  respiration  than  its  chemical 
analysis,  as  the  aqueous  vapour  contained  in  the  air  is  thereby 
taken  into  account. 

J.  J.  van  Eck  (Z.  anal.  Chem.,  1913,  p.  753)  employs  for  this 
estimation  Romijn's  water-pipette. 

OZONE. 

The  usual  qualitative  test  for  ozone  is  the  blue  colour  pro- 
duced in  a  solution  of  (or  on  a  test-paper  impregnated  with) 
potassium  iodide  and  starch,  through  the  liberation  of  iodine. 
A  special  test-paper  for  this  purpose  is  found  in  the  trade  as 
"  Houzean's  test-paper,"  improved  by  Arnold  and  Mentzel  (Ber., 
1902,  p.  1324).  Of  course  this  test  can  only  be  made  in  the 
absence  of  free  chlorine,  bromine,  hydrogen,  peroxide  or  nitrous 
vapours,  if  (as  formerly  usual)  an  acidified  solution  of  KI  is 
employed  ;  but  in  the  absence  of  chlorine  the  immediate  blue 
coloration  of  a  neutral  solution  of  KI  and  starch  is  a  good  test 
for  ozone,  since  the  colour  comes  out  only  very  slowly  in 
presence  of  hydrogen  peroxide  and  not  at  all  with  nitrites. 

Engler  and  Wild  (Ber.,  1896,  p.  1940)  test  for  the  presence 
of  ozone  by  passing  large  quantities  of  the  air  under  examination 
first  through  finely-divided  chromic  acid,  in  order  to  remove  any 
hydrogen  peroxide,  and  then  into  a  glass  tube,  in  which  are 
placed,  side  by  side,  a  manganese-sulphate  paper,  which  is 
coloured  brown  by  ozone  (through  the  formation  of  Mn3O4)  but 
not  by  chlorine,  and  a  thallous-oxide  paper,  which  remains 
colourless  in  presence  of  nitrous  acid,  but  is  turned  brown  by 
ozone.  If  both  papers  are  coloured,  ozone  is  present. 

The  qualitative  detection  of  ozone  can  be  performed  most 
easily  and  distinctively  by  tetramethyl  -  di  -/-  diaminodi- 
phenylmethane,  usually  designated  as  "  tetramethyl  base,"  either 
in  alcoholic  solution  or  as  a  test-paper.  Ozone  produces  with  it 
a  violet,  nitrogen  oxides  a  straw-yellow  coloration  ;  hydrogen 
peroxide  gives  no  reaction  (Arnold  and  Mentzel,  Ber^  1902,  pp. 
1327  and  2902 ;  F.  Fischer  and  H.  Marx,  ibid.t  1906,  p.  2555). 

A  very  complete  paper  on  the  detection  of  ozone  in  the 
presence  of  nitrogen  tetroxide  and  hydrogen  peroxide  is  that 
of  Keiser  and  M'Master  (Amer.  Chem.  /.,  1908,  p.  967). 


220  TECHNICAL  GAS-ANALYSIS 

The  quantitative  estimation  of  ozone  in  air,  etc.,  is  usually 
carried  out  by  passing  the  gas  through  a  solution  of  potassium 
iodide  and  titrating  the  iodine  set  free.  Formerly  an  acidified 
solution  was  employed,  but  this  caused  errors  up  to  an  amount 
of  50  per  cent.,  which  are,  however,  avoided  according  to 
Lechner  (Z.  Elektrochem.,  I9ii,xvii.  p.  412)  by  employing  an 
alkaline  solution  of  KI.  Czako  (J.  Gasbeleuckt,,  1912.  Iv.  p.  768) 
carries  this  method  out  in  a  Bunte  burette.  The  burette,  filled 
with  distilled  water,  is  connected  in  an  inverted  position  by  means 
of  a  mercury  seal  with  the  gas-holder,  and  about  100  c.c.  of  the 
gas  is  introduced.  After  reading  the  volume,  the  water  is 
drawn  off,  about  10  or  12  c.c.  of  the  alkaline  Kl-solution  is 
introduced,  the  burette  is  shaken  for  three  minutes,  its  contents 
are  run  into  a  flask  and  the  burette  is  rinsed.  The  absorbing 
liquid  is  acidulated  with  5  c.c.  of  fifth-normal  sulphuric  acid, 
and  the  separated  iodine  is  titrated  with  sodium  thiosulphate. 
This  method  is  applicable  wherever  the  gas  contains  upwards  of 
o-oi  vol.  per  cent.,  i.e.,  0-02  mg.  in  100  c.c.  For  smaller 
concentrations  he  employs  a  bottle  filled  with  glass  beads,  inter- 
posed between  the  source  of  ozone  and  the  gas-meter.  The 
reaction  is  : 


One  c.c.  N/iooo  sodium  thiosulphate  solution  (0-2483  g.  per 
litre)  indicates  0-024  mg.  O3. 

Tread  well  and  Anneler  (Z.  anorg.  Chem.,  1905,  Ixviii.  p.  86) 
also  recommend  this  method,  so  do  Rothmund  and  Burgstaller 
(Chem.  Zentralb.,  1913,  i.  p.  2178),  who  estimate  ozone  and 
hydrogen  peroxide  alongside  of  each  other  by  allowing  a  weak 
acid  to  act  upon  potassium  bromide,  adding  potassium  iodide  in 
slight  excess,  and  titrating  the  iodine,  set  free  by  the  ozone,  by 
means  of  sodium  thiosulphate. 

Brach  (Chem.  Zeit.>  1912,  p.  1325)  employs  for  the  estimation 
of  ozone  apparatus,  composed  with  ground-glass  connections, 
silk  tubes  impregnated  with  wax,  and  flexible  steel  pipes. 

Krueger  and  Moeller  (Phys.  Zsch.  1912,  xiii.  p.  729;  Chem. 
Zentralb.,  1912,  ii.  p.  748)  employ  for  the  analytical  estimation  of 
ozone  its  strong  absorption  within  the  wave  lengths  200  to 
300  mm.  They  assert  this  optical  method  to  be  essentially 
more  delicate  than  any  chemical  methods, 


HYDROGEN  PEROXIDE  221 


HYDROGEN  PEROXIDE. 

The  investigations  of  Schone  (Z.  anal.  Chem.,  1894,  xxxiii. 
p.  137)  are  the  most  important  in  this  direction.  As  reactions 
for  this  compound  he  describes,  first,  the  blue  coloration  of  per- 
chromic  acid,  caused  by  adding  a  trace  of  potassium  bichromate 
to  the  solution,  covering  this  with  a  layer  of  ether,  and  shaking 
up  with  a  trace  of  sulphuric  acid  ;  secondly,  the  blue  coloration 
with  potassium  iodide  and  starch  on  addition  of  a  trace  of 
ferrous  sulphate  (Schonbein)  ;  thirdly,  the  blue  colour  produced 
by  guajacol-malt  extract.  Details  in  Lunge-Keane's  Technical 
Methods,  i.  pp.  879  et  seq. 

Determination  of  Ozone  and  Hydrogen  Peroxide  in  the  Presence 
of  each  other. — Rothmund  and  Burgstaller  (Wiener,  Monatshefte, 
1913,  xxxiv.  p.  693 ;  Amer.  Abstr.,  1913,  p.  2528)  employ  molybdic 
acid  as  a  catalyser  in  the  reaction  between  the  hydrogen  per- 
oxide and  potassium  iodide.  At  a  temperature  of  about  o°  the 
weakly  acid  solution  (about  ooi  normal)  is  added  to  a  potassium 
bromide  solution,  potassium  iodide  in  excess  of  the  amount 
equivalent  to  the  ozone  present  is  added,  and  the  free  iodine 
titrated  with  a  centinormal  solution  of  sodium  thiosulphate. 
The  amount  of  ozone  is  calculated  from  this.  Next  are  added 
10  cm.  of  seminormal  potassium  iodide  solution,  i  cm.  of 
decinormal  sodium  molybdate  solution,  and  15  cm.  of  dilute 
sulphuric  acid  (1:5  water).  After  five  minutes  the  liberated 
iodine  is  titrated,  and  the  equivalent  amount  of  H2O2  calculated. 

Pring  (Chem.  Neivs,  1914,  vol.  109,  p.  73),  as  the  result  of 
work  done  on  the  estimation  and  distinction  of  ozone,  nitrogen 
peroxide,  and  hydrogen  peroxide  at  high  dilutions,  states  that 
the  reaction  of  potassium  iodide  on  those  substances  shows  the 
following  characteristics : — With  ozone  the  ratio  of  the  different 
products  formed  is  a  function  of  the  concentration  of  the  gas 
and  of  the  total  amount  passed.  With  a  very  dilute  gas  no 
iodate  is  formed  by  only  hypoiodite  and  free  iodine,  and  no 
potassium  hydrate.  But  at  temperatures  below  —27°  this 
relation  does  not  hold. 

With  nitrogen  peroxide  mainly  iodate  is  formed,  whatever 
the  dilution  of  the  gas.  In  presence  of  an  acid  solution  of 
potassium  iodide,  nitrogen  peroxide,  even  when  present  in 
minute  quantities,  continually  liberates  iodine  from  the  reagent 


222 


TECHNICAL  GAS-ANALYSIS 


in  the  presence  of  air,  which  is  a  very  delicate  test  for  this 
gas. 

Hydrogen  peroxide,  at  high  dilution,  reacts  with  potassium 
iodide  like  ozone,  but  a  distinction  can  be  made  between  these 
gases  by  means  of  a  solution  of  tetanium  sulphate  in  sulphuric 
acid,  which  becomes  yellow  in  presence  of  very  little  hydrogen 
peroxide,  but  is  unaffected  by  ozone. 

CARBON  DIOXIDE. 

This  compound  can  be  estimated  by  most  apparatus  for 
technical  gas-analysis  described  in  previous  chapters,  and  in 
this  place  we  mention  only  some  apparatus  and  methods 
specially  intended  for  it. 

The  apparatus  of  Cl.  Winkler  (Techn.  Gas- Analysis,  p.  91), 


FIG.  95- 

shown  in  Fig.  95,  is  specially  intended  for  the  estimation  of 
small  quantities  of  CO2  in  the  air  of  coal-pits,  wells,  caves, 
subsoil,  tombs,  in  chimney-gases  poor  in  CO2,  and  analogous 
cases.  It  is  almost  identical  with  Lindemann's  apparatus  for 
the  estimation  of  oxygen  (p.  212,  Fig.  93),  but  in  the  place  of  the 
phosphorus-vessel,  used  in  the  latter,  it  contains  a  cylinder  B, 


CARBON  DIOXIDE 


223 


filled  with  glass  tubes  for  increasing  the  absorbing  surface,  the 
bottle  below  being  charged  with  a  solution  of  caustic  potash. 
The  manipulation  is  just  like  that  of  Lindemann's  apparatus. 

The  apparatus  of  A.  Lange,  intended  for  estimating  CO2  in 
liquid  carbon  dioxide  and  in  the  natural  sources  of  this  gas,  has 
been  described  supra,  p.  55. 

PettenkofeSs  classical  method,  which  is  specially  intended 
for  hygienic  purposes,  is  described  in  Lunge-Keane's  Technical 
Methods,  i.  pp.  870  et  seq. ;  also  Haldane's  apparatus,  pp.  873 
et  seq.,  and  that  of  Lunge  and  Zeckendorf  for  the  approximate 
determination  of  CO2  in  air,  p.  875. 

Ludwig  W.  Winkler  (Z.  anal.  Chem.,  1913,  p.  421)  recommends 
Pettenkofer's  method  as  most  convenient  for  the  estimation  of 
CO2  in  air,  and  describes  a  special  apparatus  for  that  purpose. 

We  shall  in  this  place  describe  the  modification  of 
the  Pettenkofer  method,  intro- 
duced by  Hesse  (Eulenberg's  Vier- 
teljahrsschrift  f.  gerichtl.  Medizin, 
N.  F.,  xxx.  p.  2 ;  translated  in 
Dennis'  Gas- Analysis,  p.  378),  as 
it  has  proved  itself  to  be  very 
satisfactory.  The  CO2  in  a  known 
volume  of  air  is  absorbed  by  a 
solution  of  barium  hydroxide  of 
known  strength,  and  the  excess  of 
Ba(OH)2  is  determined  by  titration 
with  oxalic  acid,  with  phenolphtha- 
lein  as  indicator.  For  this  method 
the  following  solutions  are  used : 
(i)  A  solution  of  i  kg.  barium 
hydroxide  and  50  g.  barium  chloride  in  5  litres  of  distilled 
water ;  (2)  a  dilute  solution  of  barium  hydroxide,  prepared 
by  adding  30  c.c.  of  the  solution  No.  I  to  a  litre  of  water, 
or  else  by  directly  dissolving  1-7  g.  of  a  mixture  of  20 
barium  peroxide  +  I  barium  chloride  in  i  litre  of  water,  and 
adding  phenolphthalein  up  to  a  faint  pink  colour.  This 
solution  is  kept  in  a  bottle,  Fig.  96,  through  the  cork  of  which 
passes  (i),  a  tube  leading  to  a  small  bottle  A,  containing  a 
caustic  potash  solution,  for  the  purpose  of  freeing  the  entering 
air  from  carbon  dioxide ;  (2),  a  syphon-tube  B,  continued  into 


B  -- 


u 


FIG.  96. 


224  TECHNICAL  GAS-ANALYSIS 

an  india-rubber  tube  with  stopcock  C  ;  (3)  a  solution  of  5-6325  g. 
of  crystallised  oxalic  acid  in  I  litre  of  water,  I  c.c.  of  which 
is  equivalent  to  I  c.c.  of  CO2 ;  (4)  a  solution  of  I  part 
phenolphthalein  in  250  parts  alcohol. 

The  samples  of  air  are  collected  in  thick- walled  Erlenmeyer 
flasks  of  100  to  500  c.c.  capacity,  supplied  with  tightly-fitting, 
double-bore  rubber  stoppers.  The  openings  in  the  stoppers  are 
closed  by  pieces  of  glass  rod,  rounded  at  the  lower  end  and 
widened  at  the  upper  end.  The  apparatus  further  comprises  a 
10  c.c.  pipette,  and  a  burette  of  10  to  15  c.c.  capacity,  graduated 
in  yV  c.c.,  with  glass  stopcock  and  a  tip  8  cm.  long. 

The  samples  of  air  are  collected  by  completely  filling  the 
flasks  with  distilled  water  of  the  same  temperature  as  the 
surrounding  air,  pouring  out  the  water  and  immediately  inserting 
the  rubber  stoppers,  care  being  taken  that  the  flask  is  not 
warmed  by  the  hand,  and  that  no  air  exhaled  by  the  operator 
gets  into  it. 

In  the  laboratory  the  glass  plug  is  removed  from  the  end  of 
the  rubber  tube  C,  Fig.  96,  the  tip  of  the  10  c.c.  pipette  is 
inserted,  the  pinchcock  is  opened,  and  some  of  the  solution  of 
barium  hydroxide  is  drawn  up  in  the  pipette,  which  is  thereby 
rinsed,  and  is  reinserted  in  the  tube,  whereupon  barium  hydroxide 
solution  is  drawn  up  to  the  zero  mark  and  the  pinchcock  is 
closed.  The  contents  of  the  pipette  are  then  run  into  the  flask, 
the  air  from  this  being  allowed  to  escape  by  momentarily 
removing  the  glass  plug  from  the  other  hole  of  the  stopper. 
The  last  drops  of  the  baryta  solution  in  the  pipette  are  driven 
out  by  closing  its  upper  end  with  the  finger,  and  warming  its 
wider  portion  with  the  hand.  The  pipette  is  then  removed,  and 
the  stopper  closed  with  the  glass  plug.  The  closed  flask  is 
allowed  to  stand  from  fifteen  to  twenty  minutes  with  occasional 
shaking.  The  barium  hydroxide  should  be  present  in  such 
excess  that  not  more  than  one-fifth  of  it  reacts  with  CO2.  If, 
therefore,  a  large  sample  of  air  is  employed,  or  if  the  CO2 
contained  in  it  is  unusually  high,  20  or  25  c.c.  of  the  solution  of 
barium  hydroxide  should  be  used. 

The  strength  of  the  baryta  solution  is  determined  by  filling 
the  burette  to  the  mark  with  the  standardised  solution  of  oxalic 
acid  (supra,  No.  3),  inserting  the  tip  of  the  burette  through  one 
opening  of  a  two-hole  rubber  stopper,  placing  this  in  the  neck 


CARBON    DIOXIDE  225 

of  a  looc.c.  flask,  and  then  running  into  this  oxalic  acid  solution 
almost  sufficient  to  neutralise  10  c.c.  of  the  baryta  solution. 
Ten  c.c.  of  the  latter  is  then  introduced  into  the  flask  in  the 
manner  above  described,  and  more  oxalic  acid  is  then  carefully 
added  until  the  pink  colour  of  the  indicator  just  disappears. 
This  colour  will  frequently  reappear  on  standing,  but  no  notice 
should  be  taken  of  this. 

The  excess  of  barium  hydroxide  in  the  sample  flask  is  then 
titrated  by  filling  the  burette  to  the  mark  with  the  oxalic  acid 
solution,  inserting  its  tip  through  one  of  the  openings  of  the 
stopper  and  running  in  the  oxalic  acid,  first  rapidly,  afterwards 
drop  by  drop.  The  increase  of  pressure  in  the  flask  is  from 
time  to  time  relieved  by  momentarily  lifting  the  glass  plug  in 
the  other  hole  of  the  stopper.  As  before,  the  end-point  of  the 
reaction  is  the  first  disappearance  of  the  pink  colour. 

The  temperature  and  barometric  pressure  of  the  outer 
atmosphere  are  then  read ;  10  c.c.  is  deducted  from  the  volume 
of  the  sample  flask  to  allow  for  that  of  the  baryta  solution 
introduced,  and  the  remaining  volume  corrected  to  standard 
temperature  and  pressure.  The  number  of  cubic  centimetres  of 
the  oxalic  acid  solution  required  to  neutralise  the  excess  of  the 
baryta  solution  is  deducted  from  the  volume  of  oxalic  acid 
required  to  neutralise  10  c.c.  of  the  baryta  solution.  If  we  call 
this  difference  =  n,  the  amount  of  carbon  dioxide  in  the  sample 
is  calculated  by  the  following  formula :  „ 

n/io  volume  of  air  sample  =  x:  10,000, 

in  which  x  represents  the  parts  of  CO2  per  10,000  of  air. 

In  lieu  of  phenolphthalein,  Moir  (Abstr.  Amer.  Chem.  Soc., 
I913>  P-  3°92)  recommends,  as  yielding  rather  more  accurate 
results  in  titration,  benzaurine  or  thymolphthalein. 

Pfeiffer  describes  his  way  of  making  very  accurate  estima- 
tions of  carbon  dioxide  in  illuminating  gas.  The  estimation 
by  potassium  hydroxide  is  not  very  accurate,  because  this 
agent  also  tends  to  absorb  some  of  the  hydrocarbon  vapours 
present.  When  greater  accuracy  is  required,  the  CO2  is 
estimated  gravimetrically  or  volumetrically ;  the  former  by 
absorbing  it  in  a  soda-lime  tube,  the  latter  by  Pettenkofer's 
method,  absorption  in  titrated  baryta  water.  For  the  former 
method  the  gas,  if  unpurified,  must  be  first  freed  from  ammonia 

P 


226  TECHNICAL  GAS-ANALYSIS 

by  passing  it  through  dilute  acid,  and  from  tar-fog  and 
sulphuretted  hydrogen  by  passing  it  through  hydrated  ferric 
oxide.  It  is  then  passed  through  a  meter,  dried  by  calcium 
chloride,  and  passed  into  a  weighed  soda-lime  tube,  the  last 
part  of  which  is  rilled  with  calcium  chloride  to  retard  the 
moisture.  Each  gramme  of  CO2  retained  here  is  =  544  c.c.  of 
CO2,  measured  in  the  moist  state  at  15°  and  760  mm. 

For  the  volumetric  estimation  by  means  of  baryta  water, 
Pfeiffer  employs  a  bottle  of  about  2  litres  capacity,  with  a  cork 
through  which  passes  a  small  dropping-funnel  of  about  50  c.c. 
capacity  reaching  almost  down  to  the  bottom,  and  a  right- 
angled  exit-tube,  as  shown  in  Fig.  97.  The  exact  capacity  of 
the  bottle  is  determined  by  weighing  it  first  empty,  and  then 
filled  with  water,  after  removing  the  exit-tube,  and 
filling  the  stem  of  the  funnel  with  water  up  to  the 
stopcock;  the  different  weights  in  grammes  =  the 
contents  in  cubic  centimetres.  To  fill  the  bottle 
with  gas  in  the  moist  state  three  drops  of  water 
are  put  in,  the  bottle  is  inverted,  and  gas  passed  in 
through  the  dropping-funnel  and  out  through  the 
exit-tube ;  a  moderate  stream  of  gas  during  two  or 
three  minutes  will  drive  out  all  the  air.  The  exit- 
tube  is  then  removed  and  replaced  by  a  glass  plug, 
the  tap  of  the  funnel  is  closed,  and  the  gas  tube  disconnected. 
The  stopcock  is  then  again  opened  for  a  second  to  make  the 
gas  in  the  bottle  assume  atmospheric  pressure,  and  the  state 
of  the  barometer  and  thermometer  in  the  room  noted. 

When  the  gas  in  the  funnel  has  been  replaced  by  air,  50  c.c. 
baryta  water  of  known  strength  (say,  20  g.  barium  hydroxide 
per  litre)  and  a  little  phenolphthalein  solution  is  run  into  the 
funnel,  and  thence,  by  carefully  opening  the  cock,  into  the 
bottle,  washing  the  funnel  with  water,  but  taking  care  that  its 
delivery  pipe  always  remains  filled  with  water.  The  liquid  is 
easily  run  in,  since  on  the  one  hand  the  carbon  dioxide  is 
quickly  absorbed,  and  on  the  other  hand  the  gas  is  compressed 
by  the  column  of  water  standing  in  the  tube  of  the  dropping- 
funnel.  The  bottle  is  shaken  now  and  then,  and  the  absorption 
may  be  taken  as  complete  in  thirty  minutes.  Now  the  cock 
of  the  funnel-pipe  is  opened,  the  rubber  stopper  is  taken  out, 
and  any  adhering  baryta  solution  washed  into  the  bottle,  the 


CARBON  DIOXIDE  227 

liquid  adhering  to  its  walls  washed  down,  and  now  the  liquid 
at  once  titrated  in  the  bottle  itself  with  decinormal  oxalic  acid 
and  phenolphthalein. 

While  the  absorption  in  the  bottle  is  going  on,  the  titre  of 
the  baryta  solution  is  established  in  the  same  way.  The 
difference  of  both  titrations,  #,  shows  the  baryta  consumed, 
expressed  as  decinormal  solution.  One  c.c.  decinormal  baryta 
corresponds  to  0-0022  g.  CO2,  or  1-119  c.c.  CO2  at  o°  C.  and 
760  mm.  If  the  contents  of  the  bottle  in  cubic  centimetres 
is  called  v,  the  temperature  =  /,  the  vapour  pressure  of  water 
at  that  temperature  =  c,  the  height  of  the  barometer  =  b,  the 
volume-percentage  carbon  dioxide,  reduced  to  standard 
volume,  is : 

Constant.  Variant. 


_  1.119x100x760 
- 


2732;  b-c 


760(273  +  0 


If  v  has  been  measured  once  for  all,  in  lieu  of  that  part  of  the 
formula  which  is  marked  "  constant,"  a  simple  figure  is  put  in. 

Apparatus  of  Riidorff  (/.  Gasbeleucht.,  1865,  p.  358;  BerL 
Ber.  xiii.  p.  130). — This  apparatus,  which  is  very  easily  handled 
even  by  persons  not  accustomed  to  gas-analysis,  is  frequently 
employed  for  estimating  the  CO2  in  coal-gas,  especially  in  its 
unpurified  state.  The  large  volume  employed  (i  litre)  admits 
of  greater  accuracy  than  the  ordinary  methods  of  volumetric 
gas-analysis,  where  usually  only  loo  c.c.  of  gas  are  examined. 
The  apparatus  is  shown  in  Fig.  98. 

Its  principle  is :  confining  the  gas  to  be  examined  in  a 
bottle  G  of  known  capacity  under  atmospheric  pressure,  and 
absorbing  the  carbon  dioxide  by  caustic  potash  solution  which 
is  run  in  from  the  burette  P,  divided  into  \  c.c.,  placed  on  the 
bottle,  at  such  a  rate  that  the  gaseous  space  vanishing  is 
replaced  by  liquid,  i.e.y  that  the  pressure  in  the  bottle  is  not 
changed.  The  quantity  of  liquid  run  out  of  the  burette 
indicates  the  volume  of  the  CO2  absorbed. 

The  apparatus  is  made  entirely  of  glass.  The  absorbing 
bottle  G  has  at  the  top  three  necks  closed  by  glass  taps,  of 
which  A  serves  for  introducing  the  gas,  C  is  connected  with 
the  burette  P,  and  B  with  the  exit-tube.  A  and  C  are  simple 


228 


TECHNICAL  GAS-ANALYSIS 


one-bore  cocks,  B  is  a  three-way  cock,  one  of  whose  bores  is 
connected  with  the  water-pressure  gauge  M,  the  other  angular 
tail-bore  being  open  to  the  outside  air.  The  bottle  G  is 

suspended  by  means  of  the  spring- 
clamp  F  in  a  large  vessel  K,  filled 
with  water  in  order  to  keep  the 
temperature  constant.  When  ex- 
amining crude  gas,  first  hydrogen 
sulphide  and  ammonia  must  be 
removed  by  washing  the  gas  with 
a  solution  of  lead  acetate  contain- 
ing a  little  free  acetic  acid  and 
contained  in  two  washing  bottles 
in  front  of  the  apparatus.  After 
all  joints  have  been  made  gas-tight 
by  greasing  with  tallow,  the  gas 
is  passed  in  at  A,  the  air  escaping 
by  the  tail-bore  of  B ;  C  during 
this  time  is  closed.  After  passing 
the  gas  through  for  ten  minutes, 
tap  B  is  turned  180°,  so  that  now 
the  communication  with  the  outer 
air  goes  through  the  pressure 
gauge  M.  Now  tap  A  is  closed 
and  the  communication  with  the 
gas-conduit  interrupted.  If  now 
tap  B  is  placed  in  the  position 
shown  in  the  figure,  the  pressure 
gauge  M  will  indicate  any  over- 
pressure still  existing  in  the  bottle. 
This  plus-pressure  is  destroyed  by 
&***  turning  tap  B  for  a  moment  so  as 
I  to  allow  the  gas  to  escape  outside, 
1|  and  this  proceeding  is  repeated 
If  until  the  pressure  gauge  M,  when 
_  tap  B  is  again  in  communica- 

rlG.  90.  ....... 

tion  with  it,  indicates  atmospheric 

pressure  by  showing  the  same  level  of  water  in  both  arms 
of  the  U-tube  during  a  longer  observation.  Now  from  the 
burette  P,  previously  filled  up  to  the  mark  O,  potash  solution 


CARBON  DIOXIDE  229 

is  cautiously  run  into  bottle  G,  always  observing  the  pressure 
gauge  M.  At  first  this  will  show  an  increase  of  pressure 
which,  however,  rapidly  vanishes,  the  CO2  in  G  being  absorbed 
by  the  potash  solution.  This  solution  is  run  in  at  the  rate  as 
the  absorption  is  proceeding,  so  that  the  state  of  the  pressure 
gauge  is  not  essentially  altered.  Towards  the  end  a  few 
minutes  are  allowed  to  elapse,  in  order  to  make  sure  that 
there  is  no  more  change  in  the  volume  of  pressure.  The 
absorption  may  be  hastened  by  cautiously  shaking  the  bottle, 
which  for  this  purpose  is  got  hold  of  by  the  two  necks  A  and 
B,  and  taken  out  of  K.  When  the  reaction  is  finished,  so 
much  liquid  is  run  from  P  into  G  that  the  atmospheric  pressure 
is  re-established.  The  burette  P  is  read  off,  and  the  cubic 
centimetres  run  out  of  it  indicate  the  same  volume  of  CO2, 
which  is  calculated  upon  the  contents  of  bottle  G. 

The  apparatus  supplied  by  the  dealers  hold  exactly  1 130  c.c., 
and  are  provided  with  a  table  from  which  the  volume-per- 
centages of  carbon  dioxide  corresponding  to  the  cubic  centi- 
metre of  potash  solution  consumed  are  directly  read  ofT(i  c.c. 
of  liquor  =  0-0885  per  cent.  CO2) ;  e.g.,  18  c.c.  of  potash  liquor 
used  =  1-593  Per  cent.  CO2  by  volume.  (PfeifTer  considers  this 
apparatus  as  more  interesting  than  practical.) 

Gockel  (f.  Gasbeleucht.,  1912,  p.  823)  has  modified  this 
apparatus  so  as  to  have  only  one  neck  and  one  glass-tap 
with  two  bores  (sold  bv  Dr  Heinrich  Gockel  &  Co.,  Berlin, 
Louisenstrasse  21). 

Other  apparatus  for  this  purpose  have  been  described  by 
Pettersson  and  Palmquist  (Berl.  Ber.,  1887,  p.  2129,  and  in 
Z.  anal.  Chem.,  xxv.  pp.  467  to  484).  Their  apparatus  has 
been  made  more  easily  portable  by  R.  P.  Anderson  (J.  Amer. 
Chem.  Soc.,  1913,  xxxv.  p.  162)  by  reducing  its  size  to  about 
half,  and  providing  a  copper  coil,  which  dips  into  the  water 
of  the  glass  vessel,  and  allows  of  rapidly  bringing  the  tempera- 
ture of  the  gas  sample  to  that  of  the  apparatus. 

Dejeanne  (Bull.  Soc.  Chzm.,  1913,  p.  556;  Z.  angew.  Chem., 
1914,  ii.  p.  15)  absorbs  the  CO2  by  baryta  water  of  known 
strength,  converts  the  excess  of  baryta  into  chloride  by  means 
of  magnesium  chloride,  and  estimates  the  Ba  in  an  aliquot 
portion  of  the  filtrate  gravimetrically. 

Apparatus  for    the    Rapid  and  Continuous  Estimation    of 


230  TECHNICAL  GAS-ANALYSIS 

Carbon  Dioxide  in  Fire-Gases,  etc. — During  recent  years  the 
methods  and  apparatus  for  a  rapid  and  continuous  analysis 
of  gaseous  mixtures  have  come  more  and  more  into  use. 
Many  of  these,  described  in  the  technical  periodicals,  are 
not  obtainable  in  trade ;  and  in  the  following  we  shall  only 
mention  the  more  important  apparatus  of  those  which  are 
actually  employed  in  practice,  and  are  obtainable  from  special 
firms. 

In  most  cases  such  apparatus  have  been  constructed  for 
a  rapid  or  continuous  estimation  of  the  percentage  of  carbon 
dioxide  in  fire-gases,  as  a  control  of  the  firemen,  but  these 
apparatus  are  also  applicable  for  the  estimation  of  other 
gases. 

A  very  rough  but  ready  estimation  of  the  carbon  dioxide 
in  smoke-gases  can  be  made  by  ascertaining  their  specific 
gravity.  A  very  expeditious  way  of  doing  this  is  the  Gas- 
balance  of  Lux  described  supra,  p.  183  (sold  by  the  Vereinigte 
Fabriken  fur  Laboratoriumsbedarf,  Berlin  N.).  An  improve- 
ment on  this  is  the  Schnellgaswage  of  G.  A.  Schultze,  Berlin- 
Charlottenburg,  in  which  the  indications  of  a  micromanometer 
give  directly  the  percentage  of  carbon  dioxide.  The  same  firm 
also  sells  the  Smoke  Gas- Analyser  of  Krell  and  Schultze,  which 
utilises  the  same  principle  in  a  different  way.  Of  course  these 
apparatus  can  also  be  used  for  any  other  gaseous  mixtures, 
containing  constituents  of  strongly  different  specific  gravities. 

Uehling  and  Steinhart  (Fischers  Jahresber.,  1896,  p.  1166) 
estimate  CO2  by  the  velocity  of  the  gases  issuing  from  a  narrow 
orifice.  Lux  and  Precht  (ibid.,  1893,  p.  1205)  pass  the  gases 
through  a  hollow  globe.  Pfeiffer  (Ger.  P.  78612)  ;  Arndt  (Ger.  Ps. 
70829,  125470,  129613);  Dosch  (Z.  fur  chem.  Apparatenkunde, 
1907,  p.  452),  draw  the  gases  through  a  receptacle,  suspended 
from  a  balance.  So  does  Siegert  (Z.  Verein.  deutsch.  Ingen.,  1888, 
p.  1090;  1893,  p.  595),  in  whose  apparatus  the  index  of  the 
balance  indicates  directly  the  percentage  of  carbon  dioxide. 

Another  class  of  apparatus  is  that  in  which  one  of  the 
gaseous  constituents,  mostly  carbon  dioxide,  is  absorbed,  and 
the  difference  of  volume  before  and  after  absorption  is 
registered.  These  apparatus  have  the  advantage  of  very 
easy  registration,  but  the  drawback  that  they  act  not  con- 
tinuously, but  periodically,  testing  a  sample  of  gas  once  about 


CARBON  DIOXIDE  231 

every  five  minutes  and  registering  the  result,  as  the  gas  must 
be  left  in  contact  with  the  absorbing  agent  for  some  little  time. 
A  definite  volume  of  the  gas  to  be  tested  is  automatically 
drawn  off,  the  carbon  dioxide  removed  by  soda-lime  or  caustic 
potash  liquor,  and  the  volume  of  the  gas  remaining  after 
absorption  is  measured  and  registered. 

The  simplest  apparatus  of  this  class  is  that  of  Craig,  in 
which  between  two  synchronously  running  gas-meters  a  soda- 
lime  absorbing  apparatus  is  placed  ;  the  CO2-percentage  can 
be  read  off  from  the  difference  of  the  figures  indicated  by  the 
indices  of  the  meters  (Chem.  Trade  J.,  1896,  xviii.  p.  445). 

The  apparatus  of  Arndt  (Ger.  Ps.  125470  and  160288; 
Z.  Verein.  deutsch.  Ingen.y  1902,  p.  320)  is  sold  by  the  firm 
Ados,  G.m.b.H.,  of  Aachen,  by  the  name  of  Heat- effect-meter 
Ados.  It  consists  of  a  motor,  moved  by  the  chimney  draught 
or  by  a  water-jet  pump,  of  the  gas  pumps  and  the  absorbing 
apparatus  with  registering  contrivance ;  it  is  shown  in  Fig.  99. 
The  levelling  bottle  N,  filled  with  glycerin,  which  is  lifted 
by  the  motor,  on  descending  aspirates  laterally  the  smoke-gas 
to  be  tested.  When  it  has  arrived  at  its  lowest  position  (shown 
in  the  figure),  the  gas-meter  is  just  filled.  If  N  is  now  raised, 
it  forces  a  portion  of  the  gas  to  be  tested  by  D  and  E  into 
the  outer  air,  then  closes  the  entrance  channel  for  that  gas, 
and,  when  arrived  at  the  bottom  end  of  E,  shuts  off  exactly 
loo  c.c.  in  the  gas-meter.  By  the  further  rising  of  the 
glycerin,  the  gas  is  forced  into  the  absorbing  vessel  A,  which 
is  filled  with  caustic  potash  solution.  The  potash  solution, 
displaced  by  the  gas,  rises  into  the  space  B,  filled  with  air, 
and  forces  the  quantity  of  air  contained  therein  into  the 
(nearly  balanced)  diving-bell  K.  This  sets  the  registering 
apparatus  GHJ  into  motion,  and  the  position  of  the  drum  is 
marked  on  a  slowly  moving  strip  of  paper.  The  less  CO2  there 
is  in  the  gas,  the  more  air  will  be  displaced  by  the  potash 
solution  in  the  drum  B,  and  the  higher  this  drum  will  rise. 
When  the  levelling  bottle  N  has  arrived  at  the  highest  point, 
and  the  glycerin  has  risen  up  to  the  mark,  a  change  of  motion 
is  automatically  produced.  Bottle  N  goes  down,  the  glycerin 
goes  back,  the  potash  solution  in  the  absorbing  vessel  A,  the 
diving-bell  K,  and  the  liquor  in  the  gas-reservoir  return  to 
their  former  position.  The  gas  remaining  after  the  absorption 


232 


TECHNICAL  GAS-ANALYSIS 


of  the  carbon  dioxide  is  forced  into  the  outer  air  by  freshly 
aspirated  smoke-gases.  When  bottle  N  has  returned  to  the 
lowest  position,  a  new  test  is  beginning.  If  the  absorbing 
space  A  is  filled  with  phosphorous  rods,  in  the  place  of  potash 


FIG.  99. 

solution,  the  apparatus  can  serve   for   estimating   the   oxygen 
contents  of  the  gases. 

By  improvements  indicated  in  the  Ger.  P.  160288 
(Z.  angew.  Ghent.,  1905,  p.  1231)  it  is  possible  to  collect  the  gas 
always  at  atmospheric  pressure,  thus  obviating  the  entrance  of 


CARBON  DIOXIDE  233 

atmospheric  air  even  when  the  gases  are  aspirated  through  the 
apparatus  at  reduced  pressure. 

The  motor  consists  of  a  reservoir  of  liquid  with  a  movable 
bell,  which  is  almost  entirely  balanced  by  a  counterweight. 
Below  the  bell  is  the  aperture  of  a  tube  communicating  with 
the  chimney,  provided  with  an  air-valve  which  is  turned  by  the 
movement  of  the  bell  itself,  and  thus  causes  the  bell  to  go  up 
and  down.  This  movement  is  transferred  by  a  cord  and  pulley 
to  the  gas-pumps  and  sets  them  into  motion.  These  pumps 
are  bells,  diving  in  glycerin ;  when  going  up  they  aspirate  gas, 
and  when  going  down  they  force  it  into  the  absorbing 
apparatus.  A  controlling  apparatus  is  described  in  their 
Ger.  P.  238397  (Z.  angew.  Chem.,  1911,  pp.  1233  and  2166). 

On  similar  principles  are  founded  the  Heat-effect-meter 
Monopol  (sold  by  Kurt  Steinbock,  of  Frankfort-on-Maine)  and 
the  Econograph  (manufactured  by  the  Allgemeine  Feuerungs- 
technische  Gesellschaft,  Wilhelmstrasse,  Berlin  W.). 

The  Coometer  of  Schlatter  and  Deutsch  (made  by  Michael 
Pal  &  Co.,  London  S.W.,  described  by  Samter  in  Z.fiir  chem. 
Apparatenkunde^  1908,  iii.  73)  is  made  entirely  of  metal  and  makes 
four  analyses  per  minute.  The  gas  to  be  tested  is  aspirated  by 
a  pump,  then  forced  by  fine  openings  into  the  absorbing  liquid, 
and  thus  the  absorption  very  quickly  produced.  The  un- 
absorbed  gas  acts  upon  an  index  which  states  directly  the 
percentage  of  CO2  on  a  visible  disc. 

Mertens  (Amer.  P.  1060996;  J.  Ind.  and  Eng.  Ckern.,  1913, 
p.  623)  describes  an  automatic  apparatus  for  measuring  the 
percentage  of  carbon  dioxide  in  furnace-gases  by  means  of  a 
Mariotte's  bottle. 

A  further  class  of  quickly  working  apparatus  for  continuous 
gas-testing  is  on  the  principle  of  introducing  the  gas  into  the 
apparatus  by  two  conduits,  in  one  of  which  the  gaseous  con- 
stituent to  be  estimated  is  removed,  and  its  percentage  is 
indicated  by  the  difference  of  pressure  between  the  two  gaseous 
currents.  On  this  is  founded  the  Autolysator  of  Strache,  Johoda, 
and  Genzken  (Chem.  Zeit.,  1906,  p.  1128;  sold  by  the  Verein. 
Fabriken  fur  Laboratoriumsbedarf,  in  Berlin).  Its  principle  is 
shown  in  Fig.  100.  The  gas  is  aspirated  by  a  water-jet  pump 
through  a  capillary  tube,  KI}  and  by  means  of  the  regulating  tap 
H  the  difference  of  pressure,  measured  by  a  differential  pressure 


234 


TECHNICAL  GAS-ANALYSIS 


gauge,  is  kept  uniform  ;  thus  the  quantity  of  air  passing  through 
Kj  during  a  minute  is  always  the  same.  The  same  quantity  of 
gas  is  also  aspirated  by  a  second  capillary  K2,  and  between  Kx 
and  K2  the  absorbing  vessels  Al  and  A2  are  interposed.  When 
testing  for  CO2,  these  vessels  are  filled  with  soda-lime.  If  there 
is  no  CO2  in  the  gas,  the  differential  pressure  gauge  M2,  attached 
to  K2,  shows  exactly  the  same  as  the  gauge  Ml ;  this  is  the  zero 
point  of  the  division.  If  there  is  CO2  in  the  gas,  it  is  retained 


FIG.  loo. 

in  Al  and  A2,  and  through  K2  now  as  much  more  gas  must 
pass  per  minute  as  corresponds  to  the  CO2  present  in  the 
gas.  Thereby  the  difference  visible  in  the  pressure  gauge 
M2  is  increased,  and  the  percentage  of  CO2  can  be  read  off 
directly  on  a  scale.  In  the  place  of  the  regulating  tap  H  an 
automatic  regulator  of  the  difference  of  pressure  is  employed, 
and  the  connecting  pipes  Pl  and  P2  can  be  provided  with 
an  apparatus,  shown  in  Fig.  101,  which  automatically  registers 
the  differences  of  pressure  occurring  at  K2,  and  thereby 
the  CO2  percentage  of  the  gas.  Fig.  102  (p.  236)  shows 
how  the  whole  apparatus  is  arranged.  The  gas  to  be  tested 
must  be  deprived  of  dust  and  moisture  by  filtration  and 
drying,  before  entering  into  the  apparatus.  The  advantages 
claimed  for  this  apparatus  are,  first,  rapidity  of  action 
(it  indicates  the  composition  of  the  gases  every  one  to  one 
and  a  half  minutes) ;  second,  simplicity  of  construction  and 
handling;  third,  insensibility  against  shocks  and  dirt;  fourth, 
visibility  of  the  diagram  during  the  work,  and  from  a 
distance. 


CARBON  DIOXIDE 


235 


A  new  form  of  the  "autolysator"  is  described  in/.  Gasbeleucht., 

191 1,  p.  548. 

The  apparatus  of  Jones  (Amer.  P.  854696 ;  Z.  filr  chem. 
Apparatenkunde,  1908,  p.  124)  is  constructed  on  the  same 
principle  as  the  autolysator,  but  is  less  recommended  than 
this. 

Other  apparatus  for  the  same  purpose  have  been  constructed 
by  the  Dragerwerke  (Ger.  P.  236730;  Z.  angew.  Chem.,  1911, 
p.  1646) ;  Allgemeine  Feuertechnische  Gesellschaft  (Ger.  P. 
228802  ;  ibid.,  p.  82)  ;  Arndt 
(Amer.  P.  1065652;  Ger.  Ps. 
231117,232200,233225;  ibid., 
pp.  468,  7 1 o,  80 1 ) ;  Underfeed 
Stoker  Co.  (Ger.  P.  233253; 
ibid.,  p.  800) ;  Knoll  (Ger.  P. 
238503  ;  ibid.,  p.  2166)  ;  Har- 
tung  (Ger.  Ps.  238398  and 
244859;  ibid.,  pp.  2105  and 
2266,  and  1912,  p.  1445); 
Wattebled  (Ger.  P.  234185; 
ibid.,  p.  993)  ;  Arndt  (Ger.  Ps. 
241074,241075,247165;  ibid., 

1912,  pp.  79,  80,  1445) ;  Boul- 
ton    (B.    P.    5601   of    1912); 
Gaither  (/.  Ind.  Eng.  Chem., 
iv.    p.  611);    Brubaker  (ibid., 
p.  599) ;  E.  Rupp  (Chem.  Zeit., 
1912,  p.  59);  A.  Schmid  (Stahl 
u.  Risen,  1912,  xxxii.  p.  245  ; 
Chem.  Zentralb.,  1912,  i.  967); 
H.  M.  Atkinson  (Chem.  News, 
1912,  cv.  p.  136);   Henderson 

and  Russell  (Amer.  J.  Phys.,  1912,  xxix.  p.  436 ;  Chem.  Zentralb., 
1912,  i.  p.  1860) ;  Koenig  (/.  Ind.  Eng.  Chem.,  1912,  vii.  p.  844) ; 
the  Uehling  Instrument  Co.  (Metall.  Chem.  Eng.,  x.  p.  497). 

The  detection  and  estimation  of  exceedingly  minute  quantities 
of  carbon  dioxide  is  carried  out  as  follows  by  M'Coy  and 
Tashiro  ($th  Intern.  Congr.  Appl.  Chem.,  i.  361  ;  Abstr.  Amer. 
Chem.  Soc.,  1912,  p.  3243).  The  minimum  volume  of  gas 
required  to  produce  an  incipient  reaction  with  t  drop  of 


FIG.  101. 


236 


TECHNICAL  GAS-ANALYSIS 


barium  hydrate  solution  is  ascertained  by  means  of  a  specially 
constructed  glass  bulb  holding  25  c.c.  The  gas  is  introduced 
into  this  over  mercury,  and  the  volume  of  gas  needed  to  render 
turbid  a  drop  of  baryta  solution,  protruding  at  the  orifice  of  a 
tube  laterally  fused  in  the  bulb,  is  measured  by  withdrawing 
mercury  through  the  bottom  tap. 
be  detected  in  this  way. 


i -ox  io~7  g.  of  CO2  could 


FIG.  102. 

A  Carbon  Dioxide  Thermoscope  is  sold  by  the  Underfeed 
Stoker  Co.,  Ltd.,  London.  It  is  a  small  thermoscope,  easily 
handled  and  self-registering,  which  detects  the  CO2  in  a  gas  by 
measuring  the  heat  produced  by  the  action  of  CO2  on  solid 
caustic,  and  registers  the  percentage  directly  on  the  thermoscope 
scale. 

Optical  methods  for  the  testing  of  fire-gases,  etc.,  for  carbon 
dioxide.  The  Refractometer  of  Haber  has  been  already 
described  on  p.  176. 


CARBON  MONOXIDE  237 

Measurement  of  the  Heat  produced  by  the  Absorption  of 
Carbon  Dioxide  by  the  Absorbing  Reagent. — Apparatus  for  this 
purpose  has  been  described  by  Hinmann  (Ger.  P.  228784; 
Z.  angew.  Chem.,  1911,  p.  83,  and  1912,  p.  1422);  Miiller  (Ger.  P. 
233463 ;  Z.  angew.  Chem.,  1911,  p.  899,  and  1912,  p.  1422). 

The  estimation  of  carbon  dioxide  in  technical  chlorine  is 
described  later  on  in  the  chapter  dealing  with  chlorine. 

The  estimation  of  carbon  dioxide  dissolved  in  water  is 
treated  upon  by  L.  W.  Winkler  (Z.  anal.  Chem.,  xlii.  p.  735  ; 
Chem.  Zentralb.,  1904,  i.  p.  608),  who  drives  it  out  by  means  of 
hydrogen  and  absorbs  it  in  caustic  potash.  According  to 
Casares  and  Pina  de  Rubies  (Chem.  Zentralb.,  1913,  i.  p.  2177)  this 
method  is  unreliable  if  small  quantities  are  to  be  determined, 
the  deviations  amounting  to  4  mg. 

Tillmans  (/.  Gasbeleucht.,  1913,  pp.  348  and  370)  has 
examined  the  various  methods  for  estimating  CO2  dissolved 
in  water. 

CARBON  MONOXIDE. 

Qualitative  detection  of  traces  of  carbon  monoxide  in  the  air 
of  heated  rooms,  coal-pits,  etc.  (Cf.  on  this  subject  Lunge- 
Keane's  Technical  Methods  of  Chemical  Analysis,  vol  i.  pp.  889 
et  seq.}  If  blood  is  diluted  with  water  so  far  that  the  mixture 
shows  only  a  just  perceptible  pink  shade,  it  gives  a  characteristic 
absorption  spectrum,  showing  two  dark  bands  between  the  lines 
D  and  E.  If  to  this  dilute  blood  solution  a  few  drops  of  strong, 
recently  prepared  ammonium  sulphide  are  added,  those  black 
bands  vanish,  and  are  replaced  by  a  single  broad  band,  lying 
between  the  two  above-mentioned  bands.  Quite  different  from 
this  is  the  behaviour  of  blood  containing  carbon  monoxide.  To 
begin  with,  in  the  presence  of  carbon  monoxide  the  scarlet 
colour  of  blood  changes  into  pink,  and  this  solution  yields 
almost  exactly  the  same  absorption  spectrum  as  pure  blood ; 
but  the  two  bands  do  not  vanish  on  adding  ammonium  sulphide. 

H.  W.  Vogel  (as  reported  in  Treadwell's  Lehrb.  d.  analyt. 
Chemie,  ii.  p.  542)  carries  this  method  out  in  the  following 
way  : — A  100  c.c.  bottle,  filled  with  water,  is  placed  in  the  room, 
the  air  of  which  is  to  be  tested  for  CO ;  2  or  3  c.c.  of  a  very 
dilute  solution  of  blood,  which  in  the  thickness  of  the  layer 
contained  in  a  test-tube  shows  the  blood  spectrum,  is  put  into 


238  TECHNICAL  GAS-ANALYSIS 

the  bottle  which  is  closed  and  shaken  ;  a  few  drops  of  ammonium 
sulphide  are  added,  and  the  liquid  is  observed  in  the  spectroscope. 
If  the  two  bands  do  not  vanish,  carbon  monoxide  is  present. 
According  to  Vogel  up  to  0-25  per  cent.  CO  can  be  proved  in 
this  way.  According  to  Czako  (Beitrdge  zur  Kenntnis  naturlicher 
Gasausstromungen,  1913,  p.  24)  the  air  to  be  tested  for  CO  by 
this  method  should  be  first  purified  from  oxygen  by  means  of 
phosphorus  or  sodium  hydrosulphite. 

Hempel  (ibid.y  p.  542)  has  greatly  improved  this  method  by 
passing  the  gas  through  two  funnels,  connected  by  an  india- 
rubber  ring,  after  placing  a  mouse  into  the  space  thus  formed. 
The  gas  is  passed  through  this  contrivance  during  three  or  four 
hours  at  the  rate  of  10  litres  per  hour.  The  mouse  is  then 
killed  by  immersing  the  funnels  in  water,  and  a  few  drops  of  its 
blood  are  taken  out  near  its  heart,  which  are  diluted  with  water 
and  spectroscopically  tested  as  described  above.  In  this  way 
Hempel  succeeded  in  proving  with  certainty  down  to  0-032 
per  cent.  CO.  If  there  is  too  little  CO  present,  no  visible 
symptoms  of  poisoning  can  be  observed  ;  these  appear  only  if 
the  amount  of  CO  is  0-06  per  cent,  after  half  an  hour.  The 
mouse  then  exhibited  dyspnoea  and  lay  on  one  side. 

Potain  and  Drouain  (Compt.  rend.,  cxxvi.  p.  938)  prove  the 
presence  of  small  quantities  of  carbon  monoxide  by  passing 
the  gas  through  a  very  dilute  solution  of  palladium  proto- 
chloride,  whereby  metallic  palladium  is  separated:  — 


The  solution  is  decolorised  by  larger  quantities  of  CO,  or 
assumes  a  faint  grey  colour,  but  in  the  presence  of  mere  traces 
it  is  light  yellow.  In  order  to  observe  the  colour  more  distinctly, 
they  filter  it  from  the  separated  palladium,  and  compare  its 
colour  with  that  of  the  original  platinum  solution. 

Nowicki  (Chem.  Zeit.,  xxxv.  p.  1120;  Z.  angew.  Chem.,  1912, 
p.  231)  utilises  the  same  method  for  a  small  portable  apparatus, 
containing  a  strip  of  paper  moistened  with  palladium  proto- 
chloride  solution,  the  blackening  of  which  indicates  the  presence 
of  CO.  The  volume  per  cent.  CO  and  the  time  in  minutes 
up  to  complete  blackening  are  respectively  o-oio  —  1  1.60;  0-25  — 
5.32;  0-050  —  3.16;  0-075  —  2.12;  o-ioo  —  1.9;  0-250  —  11/15; 
0500—13/30;  1-000—4/15. 


CARBON  MONOXIDE  239 

Cl.  Winkler  (Z.  anal.  Ckem.,  1889,  p.  267)  describes  a  colori- 
metrical  test  for  CO.  The  gas  is  treated  with  a  solution  of  100  g. 
cupric  chloride  in  I  litre  of  nearly  saturated  sodium  chloride 
solution.  This  solution  is  colourless  or  but  slightly  brownish ; 
in  contact  with  air  it  forms  a  green  precipitate  of  cupric 
oxychloride,  but  it  keeps  unchanged  in  a  bottle  closed  by 
a  rubber  cork,  and  provided  with  a  copper  spiral  reaching  from 
top  to  bottom.  If  the  gas  to  be  examined  is  passed  through 
this  solution,  or  agitated  with  it  in  a  closed  bottle  for  some 
little  time,  most  of  the  CO  is  absorbed.  A  portion  of  the 
liquid  is  put  into  a  test-tube,  where  it  is  diluted  with  three  or 
four  times  its  volume  of  water,  without  troubling  about  the 
white  precipitate  of  cuprous  chloride  (this  is  indispensable)  ; 
then  a  drop  of  a  solution  of  sodium  palladium  protochloride 
is  added.  In  the  presence  of  the  slightest  quantity  of  carbon 
monoxide  a  black  cloud  of  finely  divided  palladium  is  formed. 
If  the  test  is  always  performed  under  exactly  similar  con- 
ditions, the  depth  of  the  black  colour  admits  of  approximately 
guessing  at  the  quantity  of  carbon  monoxide.  Thus  ooi  c.c. 
CO  =  0-0000125  g.  can  be  found.  The  presence  of  other  gases 
does  not  materially  influence  the  reliability  or  sensitiveness  of 
this  reaction.  (Treadwell,  in  his  Lehrb.  der  anal.  Chem., 
3rd  ed.,  vol.  ii.  p.  543,  declares  this  test  to  be  wrong,  because, 
as  he  convinced  himself,  a  black  precipitate  of  metallic 
palladium  is  formed  also  in  the  absence  of  carbon  monoxide, 
since  cuprous  chloride  by  itself  easily  reduces  dilute  palladium 
salts  to  metallic  palladium.) 

We  must  also  refer  to  the  testing  of  air  for  inflammable 
gases  generally,  described  in  a  subsequent  chapter,  which,  of 
course,  will  indicate  carbon  monoxide  as  well. 

Quantitative  Estimation  of  Carbon  Monoxide. — The  usual 
way  of  estimating  this  gas  is  by  absorption  in  an  ammoniacal 
or  acid  solution  of  cuprous  chloride  (supra,  p.  126  et  seq.}  by 
means  of  a  Hempel  pipette  (p.  89)  or  a  Bunte  burette,  as 
described  pp.  64  et  seq.  The  combustion  method  can  also  be 
employed  (p.  109).  L.  A.  Levy  (/.  Soc.  Chem.  Ind.^  1911,  p. 
1437)  discusses  the  estimation  of  this  gas.  According  to 
him  the  cuprous  chloride  method  neither  gives  a  sharp 
reaction,  nor  does  it  indicate  small  percentages.  A  number 
of  colorimetric  methods  has  been  described  for  the  estima- 


240  TECHNICAL  GAS-ANALYSIS 

tion  of  CO,  but  they  are  not  sufficiently  simple  and 
accurate  for  industrial  purposes.  Winkler  (Z.  anal.  Chem., 
1889,  vide  supra]  employs  for  this  purpose  the  black  cloud 
of  reduced  palladium  formed  by  shaking  up  the  gas  with 
palladium  chloride  and  cuprous  chloride.  Potain  and  Drouin 
(Comptes  rend.,  cxxvi.  p.  938)  employ  the  progressive  loss 
of  colour  experienced  by  palladium  chloride  solution  on  re- 
duction by  carbon  monoxide.  Others  employ  the  change 
of  colour  exhibited  by  dilute  blood  solution  and  the  reduction 
of  ammoniacal  silver  oxide.  Levy  himself  tried  gold  chloride 
(recommended  by  Donau,  Akad.  der  Wiss.  Wien,  cxiv.  p. 
79),  but  not  with  good  results,  as  he  explains  in  detail. 
Ultimately  he  adopted  the  method  of  Gautier  and  Clausmann 
{Comptes  rend.,  cxxvi.  p.  793;  vide  supra,  p.  127),  the 
selective  oxidation  of  carbon  monoxide  by  heated  iodine 
pentoxide,  and  observing  the  iodine  liberated,  from  which  he 
developed  the  following  method  : — The  carbon  monoxide  is 
selectively  oxidised  to  carbon  dioxide,  and  the  oxidised 
gas  is  aspirated  through  a  fixed  volume  of  standard  baryta 
solution  coloured  by  phenolphthalein,  until  the  solution  is 
decolorised  by  the  saturation  of  the  baryta,  which  corresponds 
to  a  fixed  volume  of  carbon  dioxide,  or  the  same  fixed 
volume  of  CO  oxidised  into  CO2.  An  observation  of  the 
volume  of  gas  required  to  effect  this  decolorisation  indicates 
the  percentage  of  CO.  The  following  points  must  be 
observed : — Unsaturated  hydrocarbons,  which  are  oxidised 
by  iodine  pentoxide,  must  be  first  removed,  probably  by 
a  strong  solution  of  bromine  in  potassium  bromide,  followed 
by  a  treatment  with  strong  caustic  potash  solution,  which 
also  absorbs  any  CO2  originally  present  in  the  gas ;  then 
drying  the  gas  by  passing  it  over  phosphorus  pentoxide  in 
a  tube  I  in.  in  diameter  and  4  in.  long  (which  for  various 
reasons  is  preferable  to  strong  sulphuric  acid) ;  then  passing 
the  gas  through  iodine  pentoxide,  mixed  with  small  pieces 
of  ignited  asbestos,  contained  in  a  U'tu^e>  which  is  fused 
to  another  tube  containing  copper  turnings  for  retaining 
the  iodine  liberated  from  the  pentoxide  by  the  CO,  this 
compound  Q~tuDe  being  placed  in  an  air-oven  maintained  at 
1 68°  to  i8o°C.  The  gas  now  enters  into  the  "decolorisation 
vessel  "  containing  the  baryta  solution.  This  vessel  (supplied 


CARBON  MONOXIDE  241 

by  Messrs  Alexander  Wright  &  Co.,  Ltd.,  Westminster)  is 
similar  to  a  Winkler  coil  (p.  145),  but  the  slopes  are  considerably 
steeper.  The  baryta  solution  employed  here  is  of  such  a 
strength  that  it  is  neutralised  by  the  passage  of  20  c.c.  carbon 
dioxide  measured  at  60°  F.  and  30  in.  pressure.  A  three- 
way  tap  is  interposed  before  the  last  vessel,  so  that  the  gas  may 
be  bye-passed  until  the  commencement  of  a  test.  The  gas  is 
drawn  through  the  apparatus  by  the  flow  of  water  from  an 
aspirator,  the  volume  of  the  outflowing  water  being  equal  to 
the  total  volume  of  gas  passing  through.  If  this  volume  is 
called  V  c.c.,  then  as  20  c.c.  of  carbon  monoxide  is  contained 

therein,  the  percentage  of  the  latter  is  =     v   .     For  practical 

use  the  aspirator  is  graduated  directly  in  percentages  of  carbon 
monoxide.  Experiments  quoted  in  the  paper  showed  that 
the  colorimetrical  results  obtained  with  gases  of  high  carbon 
monoxide  content  agreed  within  about  0-3  per  cent,  with 
analyses  made  by  the  most  accurate  methods. 

When  the  gas  contains  but  little  CO,  a  more  dilute  baryta 
solution  must  be  used,  but  the  absorption  in  this  case  is  not 
quite  complete.  For  the  purpose  of  getting  accurate  results 
with  gases  containing  only  traces  of  CO,  e.g.  fumes  from 
gas-stoves,  air  from  pits  or  lime-kilns,  etc.,  the  gas  is  drawn 
by  means  of  a  filter-pump  through  a  meter  and  then  through 
the  apparatus.  A  strong  baryta  solution  is  employed.  After 
a  certain  time  the  pump  is  stopped  and  the  excess  of  baryta 
back-titrated  with  oxalic  acid.  In  the  discussion  on  this 
paper,  reported  loc.  tit.,  several  speakers  expressed  doubt 
whether  this  method  would  answer  in  the  hands  of  unskilled 
persons. 

If  the  gas  remaining  after  the  estimation  of  carbon  mon- 
oxide and  removing  aqueous  vapour  and  carbon  chloride 
is  passed  through  a  combustion  tube  60  cm.  long,  half 
filled  with  cupric  oxide  and  half  with  platinum  asbestos, 
and  heated  to  a  dark  red  heat,  hydrogen  and  methane  are 
completely  burnt  to  water  and  carbon  dioxide,  which  are 
collected  as  above,  and  from  which  the  H2  and  the  CH4 
are  calculated. 

Burrell  (Science,  xxxv.  p.  423)  describes  an  apparatus  for 
this  purpose. 

Q 


242  TECHNICAL  GAS-ANALYSIS 

Haldane  (J.  Ind.  and  Eng.  Chem.,  1910,  p.  9)  describes  a 
colorimetric  method  for  the  determination  of  CO  in  air, 
founded  on  the  formation  of  oxyhaemoglobin  in  a  blood 
solution. 

Haldane  (The  Investigation  of  Mine  Air,  by  Forster  and 
Haldane,  pp.  100  and  115)  also  describes  special  apparatus 
for  the  analysis  of  mine  air,  both  in  the  laboratory  and 
in  situ. 

Other  publications  on  the  determination  of  carbon  monoxide 
are: — 

Pontag  (Z.  Unters.  Nahr.  u.  Genussm.,  1903,  674). 

Spitta  (Arch.  f.  Hygiene,  xlvi.  p.  287  \  J.  Soc.  Chem.  Ind., 
1903,  P-  652). 

Gautier  (ibid.,  1898,  p.  931  ;  J.  Gas  Lighting,  cxxi.  p.  547). 

Kinnicutt  and  Sandford  (J.  Amer.  Chem.  Soc.,  1900,  p.  14). 

Nesmjelow  (Z.  anal.  Chem.,  1909,  p.  232). 

Worrell  (Met.  Chem.  Eng.,  1913,  xi.  p.  245). 

Sinnat  and  Cramer  (The  Analyst,  1914,  p.  163). 

Seidell  (J.  Ind.  and  Eng.  Chem.,  1914,  p.  321). 

Brunck  (Z.  angew.  Chem.,  1912,  p.  2479)  employs  the 
reaction,  utilised  by  Winkler  (supra,  p.  240)  for  the  qualitative 
discovery  of  carbon  monoxide,  in  the  following  manner  for  the 
quantitative  estimation  of  small  quantities  of  it  in  gaseous 
mixtures.  Since  the  hydrogen  chloride,  formed  by  the 
reaction,  CO  +  PdCl2+H2O  =  CO2  +  Pd  +  2HCl,  in  the  presence 
of  oxygen  oxidises  a  little  of  the  reduced  metal,  this  disturbing 
reaction  is  avoided  by  the  addition  of  sodium  acetate  ;  the  free 
acetic  acid  now  formed  does  not  act  upon  the  metal.  He 
employs  a  gas-normal  solution  of  sodium  palladium  chloride, 
containing  per  litre  4-762  g.  palladium,  I  c.c.  of  which  corresponds 
to  I  c.c.  of  CO  at  o°  and  760  mm.  pressure.  The  sodium  acetate 
is  used  in  the  shape  of  a  5  per  cent,  solution,  of  which  about  half 
of  the  volume  of  the  palladium  solution  is  used.  The  apparatus 
is  extremely  simple,  and  consists  of  an  Erlenmayer  flask  closed 
by  a  twice  perforated  rubber  cork,  the  perforations  being  closed 
by  glass  rods  ending  in  bulbs.  In  that  place  of  the  neck  to 
which  the  cork  descends,  a  mark  is  made,  and  the  contents  of 
the  flask  (0-5  to  2  litres)  up  to  this  mark  are  ascertained.  The 
flask  is  rilled  with  the  gas  to  be  examined,  either  over  water  or 
in  the  dry  way,  after  replacing  the  glass  rods  by  glass  pipes, 


SULPHUR  DIOXIDE  243 

which  in  the  end  are  quickly  drawn  out  so  that  the  rods  can  be 
put  in.  In  the  same  way  the  solutions,  first  that  of  palladium 
and  then  that  of  the  sodium  acetate,  are  introduced  ;  the  volume 
of  these  solutions  is  deducted  from  the  contents  of  the  flask. 
The  reaction,  which  is  assisted  by  occasional  shaking,  is  finished 
in  at  most  an  hour.  If  the  liquid  has  remained  clear,  no  CO 
has  been  present.  Otherwise  the  precipitated  palladium  is 
collected  on  a  small  filter,  washed  with  hot  water,  dried,  and  the 
filter  is  burnt  and  the  remaining  palladium  heated  in  a  current 
of  hydrogen  for  a  short  time.  One  g.  of  Pd  answers  to  0-2624 
g.  CO  =  2ioc.c.  at  o°  and  760  mm.  This  method  yields  very 
good  results,  but  it  is  not  applicable  in  the  presence  of  hydrogen 
or  unsaturated  hydrocarbons,  which  equally  reduce  the  palladium 
compounds. 

L.  A.  Levy  (B.  P.  12841  of  1911  ;/.  Gas  Lighting,  cxxii. 
pp.  455  and  515)  estimates  the  carbon  monoxide  colori- 
metrically,  by  utilising  the  observation  of  Donau,  that  a 
solution  of  gold  chloride,  reduced  by  carbon  monoxide,  yields 
a  colloidal  solution  of  gold  of  a  ruby  colour.  He  passes 
a  certain  quantity  of  the  gas  through  a  gold  solution 
and  then  compares  the  colour  with  that  of  a  standard 
solution. 

Nicloux  (Bull.  Soc.  Chim.  [4],  xiii.  p.  947)  describes  an 
apparatus  for  extracting  the  carbon  monoxide  from  blood  with- 
out the  aid  of  a  mercurial  pump  (abstr.  in  Chem.  Zeit.,  1912,  ii., 
p.  1838). 

SULPHUR  DIOXIDE. 

We  have  already  described  the  estimation  of  this  gas  by 
the  apparatus  of  Hesse  (p.  135),  of  Reich  (p.  137),  of  Lunge  and 
Zeckendorff  (p.  142),  of  Ost  and  of  Wislicenus  (p.  150),  etc., 
etc. 

We  shall  now  describe  special  methods  proposed  for  this 
purpose. 

Seidell  and  Meserve  (/.  Ind.  and  Eng.  Chem.,  1914,  p.  298) 
estimate  sulphur  dioxide  in  air  by  titration  with  iodine. 

Ljungh  (Chem.  Zeit.,  1909,  p.  143)  employs  a  modification 
of  Reich's  apparatus,  by  which  any  required  corrections  of 
pressure  can  be  carried  out  in  a  very  simple  way.  The  outlet 
tube  b  of  the  bottle  B,  Fig.  103,  is  connected  by  a  thick-walled 


244 


TECHNICAL  GAS-ANALYSIS 


rubber  tube  with  the  tap  z,  which  is  fixed  by  a  clamp  at  the 
perpendicular  brass  rod  s,  so  that  it  can  be  adjusted  to  the 
changing  level  of  water  in  B.  The  manipulation  is  similar  to 
that  with  Reich's  apparatus.  Tap  h  makes  connection  with  the 

gas  containing  SO2 ;  bottle  A  re- 
ceives a  measured  volume  of  deci- 
normal  iodine  solution,  say  10  c.c. 
After  closing  it,  tap  i  is  opened 
and  the  point  of  rod  s  is  put  on 
the  same  height  as  the  water-level 
in  B.  Now  h  is  opened,  so  that 
the  gas  passes  through  a  into  A ; 
the  non-absorbed  gas  goes  into  B, 
and  the  water  displaced  by  it  is 
collected.  At  the  moment  when 
the  iodine  solution  A  is  decolorised, 
h  is  closed,  and  soon  after  the  flow 
of  water  from  B  ceases.  Now  point 
s  is  again  placed  on  a  level  with 
the  water  in  B,  whereby  a  little 
water  is  made  to  run  off,  and  the 
volume  of  the  water  displaced  is 
measured.  The  calculation  of  the 
results  is  made  just  as  in  the 
case  of  the  Reich-Lunge  apparatus  shown  supra,  p.  138. 

Estimation  of  Sulphur  Dioxide  in  the  Presence  of  Nitrous 
Vapours,  e.g.  in  the  Gases  of  Vitriol- chambers. — In  presence  of 
sensible  quantities  of  nitrous  acid,  Reich's  method  and  its 
congeners  are  not  directly  applicable;  too  much  gas  is  then 
used  for  the  test,  and  its  percentage  of  SO2  is  therefore 
underestimated.  This  is  caused  by  the  fact  that  the  HJ  formed 
by  the  reaction  is  reduced  to  J  by  the  nitrous  acid.  To  avoid 
this,  Raschig  (Z.  angew.  Chem.y  1909,  p.  1182)  adds  to  the 
ordinary  charge  of  Reich's  apparatus  (consisting  of  10  c.c. 
decinormal  iodine  solution,  100  c.c.  water,  and  a  little  starch 
solution)  10  c.c.  of  a  cold  saturated  solution  of  sodium  acetate. 
The  test  is  carried  out  in  the  usual  manner,  as  described, 
p.  137,  but  the  gases  are  passed  through  a  tube  containing 
glass-wool,  in  order  to  prevent  any  droplets  of  sulphuric  acid 
getting  into  the  iodine  solution.  In  this  case  there  is  no 


FIG.  103. 


SULPHUR  DIOXIDE 


245 


FIG.  104. 


"  after-blueing,"  as  sodium  nitrite  and  sodium  sulphite  do  not 

act  upon  each  other.     This  method  admits  of  estimating  the 

nitrous  gases  as  well,  by  adding,  after  the  estimation  of  SO2, 

a  drop  of  phenolphthalein  to  the  decolorised 

liquid,  and  titrating  with  decinormal  caustic 

alkali  till  a  red  colour  appears.     From  the 

cubic  centimetres  of  decinormal  alkali  10  c.c. 

must  be   deducted  for  the  HJ  formed,  and 

10  c.c.  for  the   H2SO4  formed  according  to 

the  equation  given  supra,  p.  140.    The  excess 

of  decinormal   alkali   over   and    above    this 

20  c.c.  indicates   the   nitrous   or   nitric  acid 

present. 

For  the  estimation  of  total  acids,  SO2-fSO3 

(cf.  above,  p.    141),  Lunge  recommends  the 

bottle  shown  in  Fig.  104.  The  inlet-tube  is  closed  at  the 
bottom  and  the  portion  immersed  in  the 
solution  pierced  by  a  number  of  small 
holes,  whereby  the  stream  of  gas  is  sub- 
divided. This  bottle  is  also  employed 
for  estimation  of  SO2. 

Fig.  105  shows  the  absorption  flask 
employed  by  the  English  alkali  inspec- 
tors (34//*  Report,  for  1897,  p.  22),  which 
gives  good  results  even  in  the  most 
difficult  cases,  e.g.  in  the  absorption  of 
acid  fog.  It  cannot  be  used  for  iodine 
solution,  on  account  of  the  rubber 
stopper,  but  it  is  very  suitable  for  the 
just-mentioned  Lunge  test,  also  for  the 
absorption  of  hydrochloric  acid,  and  in 
many  other  cases.  The  figure  shows 
the  apparatus  in  half  the  actual  size.  It 
is  a  flask  fitted  with  a  rubber  stopper 
provided  with  an  inlet-  and  an  exit-tube 
as  shown.  The  former  is  8  mm.  wide, 
closed  at  the  bottom  and  pierced  with 
a  number  of  small  holes,  through  which 

the  gas  passes  to  the  double  bulb,  which  is  attached  to  the  tube 

by  a  rubber  stopper.    The  upper  bulb  is  filled  with  small  cuttings 


246  TECHNICAL  GAS-ANALYSIS 

of  rubber  tubing,  kept  in  motion  by  the  stream  of  gas,  which 
is  thus  brought  into  very  intimate  contact  with  the  absorbing 
solution  ;  the  lower  bulb  is  open  at  the  bottom.  The  success 
of  the  apparatus  depends  largely  on  the  correct  dimensions 
being  adhered  to.  The  lower  opening  of  the  double  bulb  is 
6  mm.  in  diameter,  the  lower  bulb  15  mm.  and  the  upper  bulb 
1 8  mm.  in  diameter,  and  the  upper  opening,  through  which 
the  inlet-tube  passes,  13  mm.  wide.  The  gas  passes  from  the 
bulb  into  the  flask  through  several  small  holes,  and  finally 
leaves  it  through  the  exit-tube,  which  is  narrowed  below  and 
widened  above  to  form  a  cylindrical  chamber;  the  lower, 
narrow  portion  is  filled  with  rubber  rings,  and  the  upper,  wider 
portion  with  glass-wool.  When  used  for  the 
absorption  of  acid  vapours,  the  exit-tube  is 
moistened  with  water  coloured  by  methyl  orange, 
which  serves  to  indicate  whether  complete  ab- 
sorption is  being  effected  in  the  bottle. 

Henz  (Z.  angew.  Chem.,  1905,  p.  2002)  recom- 
mends for  the  estimation  of  total  acids  in  waste 
gases  the  vessel  shown  in  Fig.  106,  which  is  half- 
filled  with  glass  beads.  It  is  charged  with  25 
c.c.  standard  alkali ;  a  certain  quantity  of  gas, 
measured  by  running  water  off  from  a  large 
stoneware  pot,  is  aspirated  through  this  vessel, 
the  contents  (without  rinsing  the  vessel)  poured 
into  a  beaker  and  titrated  with  acid  till  the  change 
of  colour  is  produced,  poured  back  into  the  vessel,  blown  out 
into  the  beaker,  and  the  titration  finished. 

Of  course  for  the  purpose  in  question  the  various  absorbing 
apparatus  specially  intended  for  poor  gases,  as  described  on 
pp.  145  et  seq.y  can  be  employed. 

Lunge  (Z.  angew.  Chem.,  1890,  p.  567)  has  suggested 
determining  the  acidity  of  kiln-gases  by  measuring  their  specific 
gravity,  a  method  which  might  be  developed  to  give  a  con- 
tinuous graphic  record  of  the  operation  of  the  furnace. 
Difference  of  I  per  cent,  of  sulphur  dioxide  by  volume  affect 
the  specific  gravity  in  the  second  decimal  place.  Such  modifi- 
cations might  be  made  by  a  modification  of  the  Lux  gas-balance 
(supra)  p  183),  which,  however,  as  at  present  constructed  is  not 
suitable  for  use  with  acid  gases,  or  by  the  aid  of  F.  C.  Muller's 


SULPHUR  DIOXIDE  247 

method  of  determining  the  density  of  gases  (ibid.,  p.  513).  The 
"Ados"  apparatus  (p.  231)  or  the  "  Autolysator  "  (p.  233)  might 
also  be  employed.  This  proposal  does  not  seem  to  have  been 
worked  out  in  practice. 

The  electric  conductivity  of  aqueous  solutions  of  sulphur 
dioxide  is  employed  for  estimating  the  SO2  in  the  air  by 
Kullgren  (/.  Chem.  Soc.  Abstr.,  vol.  civ.  p.  525). 

Estimation  of  Sulphur  Dioxide  and  Sulphur  Trioxide  along- 
side of  each  other,  e.g.  in  roaster-gases  catalysed  by  platinum. 

Bodenstein  and  Pohl  (Z.  Electrochem.,  1905,  p.  378)  pass 
such  gases  into  a  measured  quantity  of  iodine  solution,  retitrate 
the  remaining  free  iodine  with  thiosulphate  solution,  and  thus 
obtain  the  quantity  of  SO2  not  converted  into  SO3.  By  titrating 
the  decolorised  solution  with  baryta  solution  they  determine 
the  total  acidity,  which  is  partly  due  to  the  SO3  formed  by 
catalysis,  and  partly  to  the  acids  formed  by  the  reaction : 

S02  +  I2  +  2H2O  =  2HI  +  H2S04. 

Eugene  Richter  (Z.  angew.  Chem.,  1913,  132)  has  not  obtained 
satisfactory  results  by  this  method ;  he  prefers  condensing 
the  SO3  by  cooling  the  gases  down  to  ordinary  temperature, 
dissolving  the  SO3  in  water,  and  precipitating  the  sulphuric  acid 
formed  by  barium  chloride. 

Kastle  and  McHargue  (Amer.  Chem.  /.,  1907,  p.  38;  Chem. 
News,  xcvi.  p.  237)  proceed  in  a  similar  way,  but  they  determine 
the  total  acidity  by  titration  with  decinormal  sodium  hydrate 
solution  and  phenolphthalein. 

If   we   call    the  cubic    centimetres   of   decinormal    iodine 
consumed  a,  and  the  cubic  centimetres  of  decinormal  causti 
soda  (or  baryta)  b,  the  quantity  (in  grammes)  of  unchanged 
SO2  =  x  is    0-003204    a,   and   that   of    the   SO3  formed  y  = 
0-004004  (b  —  2a).     The  percentage  yield  of  SO3  is  : 

(b  —  20)  x  100 
b-a 

Ljungh  (Chem.  Zeit.,  1909,  p.  143)  prescribes  estimating  the 
loss  of  SO3  in  the  exit-gases  from  making  SO3  by  contact 
processes  by  aspirating  a  slow  current  of  gas  through  a 
measured  quantity  of  seminormal  caustic  soda,  retitrating  the 
unconsumed  soda  with  normal  acid  and  methyl  orange,  and 


248  TECHNICAL  GAS-ANALYSIS 

running  the  liquid,  diluted  up  to  a  certain  volume,  into  a 
measured  volume  of  i/ioo  normal  iodine,  to  which  a  little 
starch  has  been  added,  up  to  decolorisation.  We  abstain  from 
quoting  his  way  of  calculating  the  result,  as  the  process  is  quite 
faulty,  since  the  absorption  of  SO2  by  caustic  soda  in  the 
presence  of  oxygen  causes  the  formation  of  much  sulphuric 
acid,  and  thus  makes  the  results  of  converting  the  SO2  into  SO3 
appear  too  favourable. 

Hawley  (Eng.  and  Min.  /.,  xciv.,  p.  987)  avoids  the  errors 
connected  with  indirect  methods  by  filtering  the  SO3  out  from 
the  SO2  and  then  determining  it.  The  gas  is  drawn  through 
two  glass  funnels,  which  are  connected  together  with  their  large 
ends.  Between  the  funnels  a  sheet  of  moist  filter-paper  is 
inserted  on  which  the  SO3  is  condensed.  At  the  end  of  the 
process  the  SO3  is  washed  into  a  beaker  and  titrated  with 
decinormal  soda  solution  and  methyl  orange. 

SULPHURETTED  HYDROGEN  (HYDROGEN  SULPHIDE). 

Detection. — This  is  especially  important  in  the  manufacture 
and  control  of  illuminating  gas.  The  purified  gas,  as  it  goes  in 
the  street  mains  to  the  consumers,  ought  to  be  completely  free 
from  H2S.  In  order  to  ascertain  this,  a  large  quantity,  say 
1000  litres  of  street-gas,  is  carried  over  lead-paper,  moistened 
with  water  or  dilute  liquor  ammoniae,  which  is  blackened  by 
the  formation  of  PbS.  If  this  happens  after  all,  and  a 
quantitative  estimation  is  required,  the  volumetric  absorption 
by  cadmium  chloride  in  any  one  of  the  well-known  apparatus 
(Hempel,  Bunte,  etc.),  or  else  the  following  method,  can  be 
applied. 

Ganassini  (Boll.  chim.  farm.,  1902,  p.  417)  employs  for  the 
detection  of  H2S  its  reaction  with  ammonium  molybdate.  The 
reagent  is  prepared  by  dissolving,  on  the  one  hand,  1-25  g.  of 
ammonium  molybdate  in  50  c.c.  of  water,  on  the  other  hand 
2-5  g.  potassium  sulphocyanate  in  45  c.c.  of  water,  mixing  these 
two  solutions  and  acidifying  with  5  c.c.  of  concentrated  hydro- 
chloric acid.  The  solution  is  stable  for  some  days,  if  kept  in  a 
stoppered  bottle  and  protected  from  the  light.  It  is  employed 
by  moistening  the  inside  of  a  small  porcelain  dish  and  allowing 
the  gas  to  impinge  upon  it ;  or  by  dipping  a  piece  of  filter- 


SULPHURETTED  HYDROGEN  249 

paper  into  the  reagent  and  holding  this  in  the  gas.  If  hydrogen 
sulphide  is  present,  a  more  or  less  interior  pink  colour  is 
produced,  which  is  not  the  case  with  acetylene  or  sulphur 
dioxide. 

Quantitative  Estimation. — In  crude  coal-gas  sulphuretted 
hydrogen  is  always  present  up  to  I  per  cent,  by  volume,  and 
it  is  just  one  of  the  principal  objects  of  purifying  the  gas  to 
remove  the  H2S  by  ferric  hydroxide,  lime,  etc.  Therefore  its 
quantity  in  crude  gas  must  be  determined,  for  which  purpose 
the  following  methods  are  employed  : — 

i.  Gravimetric  Estimation. — Fresenius  (Quant.  Analysis,  7th 
ed.,  vol.  i.  p.  383)  employs  as  absorbent  pumice  -  stone 
saturated  with  cupric  sulphate.  The  absorbent  is  prepared  by 
pouring  over  60  g.  pumice,  in  pieces  of  the  size  of  a  pea,  a 
solution  of  30  g.  cupric  sulphate,  evaporating  to  dryness,  while 
stirring  the  mass,  and  heating  to  150°  for  four  hours.  A 
(J-tube  is  filled  with  this  mass  for  five-sixths  of  its  length,  the 
last  sixth  being  filled  with  dry  calcium  chloride.  The  crude 
gas  must  be  completely  purified  from  tar  by  means  of  a 
large  drying  cylinder  filled  with  cotton  -  wool ;  after  this 
comes  another  absorbing  bottle,  filled  with  moistened  vitreous 
phosphoric  acid  for  retaining  any  traces  of  ammonia,  and  a 
calcium  chloride  tower  for  completely  drying  the  gas.  This  is 
now  passed  through  a  tared  (J~tuke,  filled  with  the  copper- 
sulphate  pumice,  where  the  H2S  is  retained  (it  is  best  to  use 
two  such  (J -tubes  in  succession),  which  is  indicated  directly  by 
the  increase  of  weight.  At  last  comes  a  gas  meter  for 
ascertaining  the  quantity  of  gas  examined.  When  testing 
street-gas,  at  least  i  cb.m.  must  be  employed ;  for  crude  gas 
much  less  is  sufficient.  At  the  end,  dry  air  is  drawn  through 
the  apparatus.  Each  gramme  increase  of  weight  of  copper- 
sulphate  pumice  indicates  681-3  c-c-  H2S  at  15°  and  760  mm., 
when  saturated  with  moisture. 

According  to  L.  T.  Wright  (/.  Soc.  Chem.  Ind.,  1885,  p.  665) 
a  more  suitable  absorbent  for  H2S  is  the  cupric  phosphate 
obtained  by  precipitating  a  solution  of  cupric  sulphate  with 
sodium  hydrogen  phosphate.  This  reagent  is  prepared  by 
adding  a  solution  of  100  g.  of  crystallised  sodium  hydrogen 
phosphate  to  500  c.c.  water,  with  constant  stirring,  to  a  solution 
of  125  g.  of  crystallised  cupric  sulphate  in  750  c.c.  water, 


250  TECHNICAL  GAS-ANALYSIS 

filtering  off  the  precipitated  copper  phosphate,  and  drying  it 
at  100°.  It  is  employed  in  a  |J-tuke,  one-sixth  of  which  is  filled 
with  calcium  chloride,  just  like  the  cupric  sulphate. 

E.  P.  Harding  and  Einer  Johnson  (/.  Ind.  and  Eng.  Chem., 
1913,  p.  836)  employ  for  the  estimation  of  H2S  in  coal-gas 
cadmium  chloride,  either  gravimetrically  or  volumetrically. 
According  to  E.  Johnson's  Amer.  P.  No.  1074795, the  gas  is 
passed  through  a  solution  of  cadmium  which  retains  the  H2S, 
the  other  gases  escaping.  From  the  absorbing  agent  the  H2S 
is  liberated  by  treating  it  with  HC1  in  vacua,  and  titrating  the 
H2S  under  reduced  pressure.  The  patent  shows  apparatus 
for  carrying  out  this  method. 

2.  Volumetric  Estimation. — According  to  Bunte  (/.  Gasbe- 
leucht.)  1888,  p.  899  ;  confirmed  by  Kast  and  Behrend,  #*#.,  1889, 
p.  159)  this  is  best  performed  by  Dupasquier's  method,  viz.,  by  a 
standard  solution  of  iodine  in  potassium  iodide,  by  the  reaction 
H2S  +  I2  =  2HI  +  S2.  The  solution  employed  contains  1-0526  g. 
iodine  per  litre,  I  c.c.  of  which  indicates  o-i  c.c.  of  H2S, 
measured  moist  at  15°  and  760  mm.  The  gas  to  be  tested, 
after  being  freed  from  tar-fog  and  ammonia,  is  passed  into  a 
completely  dry  Bunte  burette  (if  necessary,  with  the  assistance 
of  an  aspirator)  and  a  portion  of  the  gas  then  sucked  out  to 
make  room  for  the  reagents.  The  iodine  solution  is  then 
sucked  in  from  a  small  dish  so  as  to  fill  the  capillary  and  bore 
of  the  stopcock,  and  then  starch  solution  to  the  lowest  division 
mark  (—10).  By  gradually  adding  fresh  quantities  of  iodine 
and  repeated  shaking,  the  end-point  of  the  reaction  is  recognised 
by  the  appearance  of  a  permanent  blue  colour.  The  amount 
of  iodine  used  is  read  off  directly  on  the  burette,  the  amount 
remaining  in  the  capillary  being  balanced  by  that  added  before 
the  starch,  which  is  not  measured.  The  volume  of  gas  used 
is  then  determined  in  the  usual  manner. 

An  alternative  method  consists  in  employing  a  dry  bottle 
of  known  capacity  (about  500  c.c.),  closed  with  a  hollow  stopper 
capable  of  holding  25  c.c.  (A  glass  tube  of  this  capacity, 
closed  at  one  end  and  fitted  into  a  rubber  cork,  the  bottom  of 
which  is  coated  with  a  film  of  paraffin  wax,  may  be  substituted 
for  a  ground-in  stopper.)  The  gas,  purified  from  tar  and 
ammonia,  is  blown  through  the  inverted  bottle  till  all  air  is 
driven  out.  The  tube  or  stopper,  into  which  25  c.c.  of  decinormal 


SULPHURETTED  HYDROGEN  251 

iodine  solution  has  been  placed,  is  inserted  while  the  bottle 
is  still  inverted,  and  the  solution  shaken  with  the  gas ;  the 
contents  of  the  bottle  and  stopper  are  then  washed  out,  and 
the  excess  of  iodine  determined  by  titration  with  sodium 
thiosulphate  and  starch.  Each  cubic  centimetre  of  iodine 
solution  equals  1-122  c.c.  of  dry  H2S  at  o°  and  760  mm.;  the 
percentage  of  the  gas  is  calculated  in  exactly  the  same  manner 
as  indicated  for  carbon  dioxide  on  p.  227,  with  the  substitution 
of  the  figure  1-108  for  that  of  1-119  m  tne  equation. 

The  iodine  method  is  liable  to  give  high  results,  since  the 
unsaturated  carbon  compounds  and  also  hydrocyanic  acid 
equally  tend  to  combine  with  iodine.  In  the  case  of  coal-gas 
the  error  thus  caused  is  usually  small,  but  it  is  very  considerable 
in  the  case  of  oil-gas  and  of  carburetted  water-gas,  owing  to 
the  presence  of  cyclopentadien,  C5H6  (Ross  and  Race,  J.  Soc. 
Chem.  Ind.,  1910,  p.  604). 

Somerville  (J.  Gas  Lighting^  1910,  p.  29)  describes  a 
modified  iodometric  method  in  which  the  gas  is  drawn  by 
means  of  an  aspirator  through  a  wash-bottle  of  100  c.c. 
capacity,  containing  10  c.c.  of  Ayiooo  iodine  solution  and  10  c.c. 
of  specially  prepared  starch  solution,  diluted  to  100  c.c.  The 
passage  of  the  gas  is  continued  until  the  blue  coloration  just 
disappears,  the  volume  of  gas  used  being  found  from  the 
volume  of  gas  run  off  from  the  aspirator.  To  obviate  the 
error  due  to  the  above-mentioned  impurities,  a  second  test  is 
made  with  the  same  gas,  which  is  first  passed  through  a  small 
tower  containing  lead  carbonate  to  remove  the  sulphuretted 
hydrogen ;  by  deducting  the  second  results  from  the  first, 
the  true  amount  of  H2S  is  found. 

3.  Colorimetric  Estimation.  —  Vernon  Harcourt  (Lunge- 
Keane's  Technical  Methods^  etc.,  vol.  ii.  p.  667)  employs  this 
method,  especially  in  cases  where  sulphuretted  hydrogen  is 
only  present  in  small  quantities.  The  gas  is  bubbled  in  a 
fine  stream  through  a  standard-sized  tube  containing  a  solution 
of  lead  oxide  in  an  excess  of  sodium  hydroxide,  with  addition 
of  sugar.  The  passage  of  the  gas  is  continued  until  the 
solution  attains  the  same  brown  colour  as  a  similar-sized 
standard  tube,  which  is  artificially  made  to  correspond  with 
the  colour  given  to  the  standard  lead  solution  by  0-0025  grains 
(0-000162  g.)  of  sulphur,  by  mixing  solutions  of  copper, 


252  TECHNICAL  GAS-ANALYSIS 

cobalt,  and  ferric  sulphates.  The  gas  is  drawn  through  the 
solution  by  an  aspirator,  the  water  run  out  being  collected  in 
a  measuring  cylinder  and  thus  indicating  the  volume  of  gas 
passed  through.  The  brown  solution  becomes  colourless  on 
exposure  to  light,  and  provided  that  carbon  dioxide  is  excluded, 
the  revivified  solution  may  be  used  over  again  for  a  considerable 
number  of  times. 

L.  W.  Winkler  (Z.  anal.  Chem.,  1913,  p.  641)  estimates  the 
hydrogen  sulphide  in  natural  waters  colorimetrically  by  means 
of  an  ammoniacal  solution  of  arsenic  trisulphide. 

Estimation  of  Sulphur  Dioxide  and  Sulphuretted  Hydrogen 
in  presence  of  each  other. 

These  gases  cannot  coexist  to  any  considerable  extent,  owing 
to  the  reaction  SO2+2H2S  =  2H2O  +  3S,  but  they  may  occur 
together  in  very  small  quantities,  e.g.  in  the  exit-gases  from  the 
Glaus  kilns.  For  the  qualitative  proof  of  the  presence  of  SO2 
in  the  presence  of  H2S,  Votocek  (Ber.,  1907,  xl.  p.  414)  recom- 
mends a  solution,  prepared  by  mixing  3  vols.  of  a  solution  of 
0-25  g.  fuchsin  (magenta)  in  1000  c.c.  water  and  i  vol.  of  a 
solution  of  0-25  g.  malachite-green,  in  1000  c.c.  water.  The 
gas  to  be  tested  is  passed  through  a  U"tuDe  containing  a 
hot  solution  of  cadmium  sulphate,  then  through  a  U~tuDe 
containing  the  above  solution,  to  which  a  little  sodium 
bicarbonate  has  been  added.  If  the  reagent  is  decolorised  and 
if  on  addition  of  acetaldehyde  a  purple  colour  is  produced, 
sulphur  dioxide  has  been  present. 

The  quantitative  estimation  of  such  a  mixture  is  founded  on 
the  fact  that,  whilst  both  H2S  and  SO2  in  contact  with  iodine 
form  2  molecules  of  HI  for  each  atom  of  sulphur  present,  the 
H2S  does  not  give  any  further  increase  in  the  acidity,  but  the 
SO2  gives  rise  to  an  equivalent  of  sulphuric  acid  ;  thus : 

H2S  +  I2  =  2HI  +  S. 
SO2  +  I2+2H20  =  2HI  +  H2S04. 

The  sum  of  H2S  and  SO2  is  measured  by  estimating  the 
quantity  of  iodine  converted  into  HI  and  the  SO2  by  the  deter- 
mination of  the  acidity  remaining  after  the  HI  thus  formed  has 
been  neutralised.  Since,  however,  the  passage  of  a  large  volume 


VOLATILE  SULPHUR  COMPOUNDS  253 

of  gas  through  iodine  solution  volatilises  a  portion  of  the  iodine, 
it  is  necessary  to  insert  a  flask  containing  sodium  hydroxide, 
or,  preferably,  sodium  thiosulphate  solution.  One  or  more 
litres  of  the  gas  are  aspirated  through  50  c.c.  of  decinormal 
iodine  solution  contained  in  a  ten-bulb  tube  (as  shown  on  p.  146, 
Fig.  72),  followed  by  a  similar  tube,  filled  with  50  c.c.  of 
decinormal  sodium  thiosulphate  solution.  When  the  operation 
is  finished,  the  contents  of  the  two  tubes  are  emptied  into  a 
beaker  and  titrated  with  decinormal  iodine  solution  and  starch ; 
the  number  of  c.c.  required  (  =  n)  multiplied  by  0-001603  gives 
the  total  sulphur  present  as  SO2  and  H2S.  The  blue  coloration 
is  then  removed  by  addition  of  a  drop  of  thiosulphate  solution, 
methyl  orange  is  added,  and  the  solution  titrated  with  deci- 
normal sodium  hydroxide  solution.  If  the  number  of  the  cubic 
centimetres  of  this,  necessary  to  neutralise  the  solution,  be 
called  m,  then  (in  —  ri)  x  0-001603  gives  the  quantity  of  sulphur 
present  as  SO2. 

OTHER  VOLATILE  SULPHUR  COMPOUNDS. 

In  coal-gas,  after  having  passed  through  the  oxide  of  iron 
purifiers,  there  are  still  small  quantities  of  volatile  sulphur 
compounds  (apart  from  any  traces  of  unabsorbed  hydrogen 
sulphide).  Most  of  this  is  carbon  disulphide,  the  amount  of 
which  varies  from  10  to  80  grains  per  100  cb.  ft.  of  gas,  accord- 
ing to  the  variety  of  coal  carbonised,  and  the  conditions  of 
distillation.  In  addition,  from  5  to  10  grains  of  sulphur  is 
present  in  the  form  of  organic  compounds,  of  which  thiophene, 
carbonyl  sulphide,  and  alkyl  mercaptans  have  been  detected. 

The  qualitative  detection  of  organic  sulphuretted  compounds, 
according  to  Ilosvay  de  Ilosva  {Bull.  Soc.  Chim.,  1890,  p.  714), 
can  be  effected  by  means  of  a  Bunsen  flame,  caused  to  strike 
back  into  the  burner,  at  the  low  temperature  of  which 
(355° to  3^o°)  tne  sulphur  is  transformed  into  hydrogen  sulphide. 
In  such  a  burner,  paper  soaked  with  lead  acetate  is  coloured 
brown  already  within  one  minute,  whilst  in  the  unchanged  gas 
such  coloration  (caused  by  H2S)  is  not  perceived  at  all,  or  only 
after  much  longer  time). 

Pfeiffer  has  also  observed  the  formation  of  H2S  from  such 
compounds  when  passing  street-gas  through  a  heated  palladium 
asbestos  tube  (p.  165). 


254  TECHNICAL  GAS-ANALYSIS 

The  detection  of  carbon  disulphide,  according  to  Vogel 
(Annalen,  1853,  p.  369),  easily  takes  place  by  passing  the 
gas,  after  drying  by  calcium  chloride,  through  a  solution  of 
potassium  hydroxide  in  absolute  alcohol,  which  causes  the 
formation  of  potassium  ethyl-xanthogenate  (xanthate) : 

/OC2H5 
CS2  +  KOH  +  C2H5 .  OH  m  CS<  +  H2O. 

NSK 

This  is  proved  by  distilling  off  the  alcohol,  slightly  acidulating 
with  acetic  acid,  and  adding  a  solution  of  cupric  sulphate,  which 
produces  a  yellow  precipitate  of  cupric  xanthogenate. 

Quantitative  Estimation  of  Carbon  Disulphide  Vapour  in 
Gases. — The  methods  proposed  by  Biehringer  (Dingl.  polyt.  /., 
cclxxvi.  p.  28),  Schmitz-Dumont  (Chem.  Zeit.,  1897,  pp. 
487  and  510),  Goldberg  (Z.  angew.  Chem.,  1899,  p.  75), 
and  Eiloart  (Chem.  News,  Hi.  p.  184)  do  not  seem  to  have  found 
much  application. 

The  conversion  of  CS2  into  xanthate  just  mentioned  as  a 
qualitative  reaction  may  be  utilised  for  a  quantitative  estima- 
tion by  ascertaining  the  quantity  of  xanthate  or  of  sulphur  in 
the  solution.  This  can  be  done  by  one  of  the  following 
methods : — 

(a)  Acidifying  with  acetic  acid  and  precipitating  by  a  deci- 
normal  solution  of  cupric  acetate  in  acetic  acid ;  the  xanthate 
precipitated  has  a  constant  composition,  the  ratio  CuO  :  CuS2 
being  1-925.     The  precipitate  is  filtered  off  and  the  excess  of 
copper   in   the   filtrate   determined    by  addition   of  potassium 
iodide  and  titration  with  decinormal  sodium  thiosulphate. 

(b)  Gravimetrically  by  boiling  the  alkaline  xanthate  solution 
with  pure  hydrogen  peroxide  solution,  whereby  the  xanthate  is 
oxidised  to  sulphate,  which  is  determined  by  barium  chloride. 

Another  method  of  estimating  the  CS2  has  been  indicated 
by  A.  W.  Hofmann  (Ber.,  xiii.  p.  1732).  A  solution  of  triethyl- 
phosphene  in  ether  is  poured  on  caustic  soda  solution,  contained 
in  three  wash-bottles,  through  which  the  gas  is  passed  for 
several  hours,  and  measured  in  the  end  by  a  meter.  In 
presence  of  CS2  the  liquid  in  the  first  bottle  soon  shows  a  pink 
colour,  and  soon  after  crystals  of  an  addition  product  oftriethyl- 
phosphene  and  carbon  disulphide  are  formed.  When  the 


CARBON  BISULPHIDE 


255 


contents  of  the  third  bottle  begin  to  turn  pink,  the  test  is 
stopped.  The  crystals  formed  are  collected  on  a  tared  filter, 
and  dried  in  vacuo.  One  g.  of  the  compound  (C2H5)3  PCS2 
indicates  0-392  g.  CS2. 

The  carbon  disulphide  may  also  be  estimated  by  converting 
it  by  platinised  pumice  into  hydrogen  sulphide,  and  estimating 
this  colorimetrically  by  Harcourt's  method,  described  supra, 
p.  251.  To  carry  out  the  test,  the  apparatus  shown  in  Fig.  107 
is  employed.  A  small  fractionating-flask  of  30  c.c.  capacity, 
filled  with  platinised  pumice,  is  placed  in  a  special  stand, 


FIG.  107. 

surrounded  by  a  glass  chimney,  so  that  the  bottom  of  the 
flask  is  about  I  in.  above  the  small  ring  burner  fixed  at  the 
bottom  of  the  chimney.  The  burner  is  lighted,  turned  down 
till  the  flame  just  shows  a  slight  luminosity,  and  the  gas  thus 
allowed  to  pass,  at  the  rate  of  \  cb.  ft.  per  hour,  through  the 
platinised  pumice,  which  is  thus  heated  to  about  300°  to 
350°  C.  After  about  ten  minutes  the  delivery  tube  is  con- 
nected to  the  tube  containing  the  lead  acetate  syrup,  and 
the  latter  to  an  aspirator,  and  the  gas  passed  in  a  thin  stream 
through  the  tube  until  this  has  reached  the  same  depth  of 
colour  as  that  of  the  standard  cylinder,  corresponding  to 


256  TECHNICAL  GAS-ANALYSIS 

0-0025  grain  or  0-000162  g.  of  sulphur.  The  volume  of  gas 
containing  this  quantity  of  sulphur  in  the  shape  of  carbon 
disulphide  is  obtained  from  the  amount  of  water  run  from  the 
aspirator  and  collected  in  the  measuring  cylinder ;  from  these 
data  the  amount  of  sulphur  present  in  the  gas  as  carbon 
disulphide  is  readily  calculated.  This  method,  whilst  very 
rapid  and  convenient,  only  gives  results  of  fair  accuracy,  if 
the  gas  tested  is  free  from  oxygen,  or  only  contains  very 
little  of  it.  Mostly,  however,  purified  coal-gas  contains 
appreciable  quantities  of  oxygen,  which,  in  presence  of  the 
hot  pumice  acts  on  the  H2S  produced,  converting  it  into 
S  and  H2O,  the  latter  condensing  in  the  delivery  tube  of 
the  flask ;  the  results  thus  obtained  are  much  below  the 
true  figure. 

CARBON  OXYSULPHIDE,  COS. 

This  gas  is  occasionally  present  in  coal-gas  (/.  Gasbeleucht^ 
1909,  p.  288).  Water  absorbs  about  one-third  of  its  volume 
of  COS.  An  aqueous  solution  of  potassium  hydroxide  absorbs 
it  very  slowly,  but  it  is  rapidly  and  in  great  quantity  taken 
up  by  a  solution  of  KOH  in  2  parts  of  water,  to  which  its 
own  volume  of  alcohol  has  been  added 

It  can  be  separated  from  carbon  disulphide  by  passing 
the  gases  through  a  mixture  of  I  part  of  triethylphosphine 
and  9  parts  of  chloroform,  which  absorbs  the  carbon 
disulphide. 

The  presence  of  COS  in  gas  mixture  can  be  detected  by 
passing  the  gas  through  a  starch  solution,  coloured  blue  by 
a  trace  of  iodine.  In  the  presence  of  COS  the  blue  tint 
changes  first  to  violet,  then  to  red,  and  finally  the  colour  is 
entirely  discharged.  Of  course  no  other  gases  must  be  present 
which  act  upon  the  iodide  of  starch. 

It  is  indirectly  detected  and  estimated  according  to  York 
Schwartz  (Chem.  Zeit.,  1888,  p.  1018),  by  first  estimating  the 
H2S  by  passing  a  considerable  quantity  of  the  gas  through 
titrated  iodine  solution,  and  then  adding  caustic  soda  solution, 
whereby  the  following  reaction  is  produced  : — 

COS +  2  KOH  =  H2S  +  K2C03. 

After  a  few  minutes  the  liquid  is  acidified,  and  the  H2S 
newly  formed  from  the  COS  is  estimated  by  iodine  solution. 


TOTAL  SULPHUR  257 

Hempel  (Z.  angew.  Chem.,  1901,  p.  865)  determines  the 
carbon  oxysulphide  in  the  presence  of  hydrogen  sulphide  and 
carbon  dioxide  by  first  absorbing  the  H2S  with  an  acid  solution 
of  cupric  sulphate,  then  decomposing  the  COS  into  CO  and  S 
by  passing  the  residual  gases  through  a  hot  platinum  capillary 
tube,  determining  the  CO  set  free  by  absorption  in  a  hydro- 
chloric acid  solution  of  cuprous  chloride,  and  finally  determining 
the  CO2  by  means  of  KOH. 

Witzek  (/.  Gasbeleucht.,  1903,  p.  145)  prefers  the  method 
indicated  by  York  Schwartz  (as  above),  which  he  quotes  from 
my  Chemisch-technische  Untersuchungsmethoden>  4th  ed.  vol.  ii. 
p.  614,  and  erroneously  designates  as  "  Lunge's  method." 

TOTAL  SULPHUR. 

In  most  cases,  the  separate  determination  of  carbon 
disulphide,  etc.,  in  coal-gas  is  not  carried  out,  as  all  the 
information  usually  required  is  obtained  by  the  estimation 
of  the  total  sulphur  present,  by  burning  a  known  volume 
of  gas  and  estimating  the  sulphur  in  the  products  of 
combustion. 

In  Great  Britain  the  method  almost  always  employed  is 
that  used  by  the  Metropolitan  Gas  Referees  for  testing  London 
gas ;  it  is  generally  known  as  the  "  Referees'  Method."  The 
gas  is  burnt  in  a  small  Bunsen  burner,  Fig.  108,  which  is 
mounted  on  a  short  cylindrical  stand,  perforated  with  holes 
for  the  admission  of  air,  and  having  on  its  upper  surface,  which 
is  also  perforated,  a  deep  circular  channel  to  receive  the  wide 
end  of  the  trumpet  tube.  On  the  top  of  the  stand  are  placed 
lumps  of  fresh  commercial  sesquicarbonate  of  ammonia, 
weighing  in  all  about  60  g.  The  upper,  narrow  horizontal 
end  of  the  trumpet  tube  is  connected  by  flexible  tubing  with 
the  side  tubulure  of  a  vertical  glass  cylinder,  constructed  above 
the  tubulure  to  about  half  its  diameter,  the  space  from  the 
contracted  neck  to  the  top  being  filled  with  glass  balls  about 
15  mm.  in  diameter,  to  break  up  the  current  of  gas  and  promote 
condensation.  To  the  top  of  the  condenser  a  long  glass  tube, 
slightly  bent  over  at  the  upper  end,  is  affixed  by  means  of 
a  cork  or  rubber  tubing ;  this  serves  to  effect  further  con- 
densation, as  well  as  to  regulate  the  draught  and  to  afford  an 

R 


258 


TECHNICAL  GAS-ANALYSIS 


exit  for  the  waste  gases.  At  the  bottom  of  the  condenser  is 
fixed  a  small  glass  tube  drawn  out  to  a  jet,  through  which  the 
liquid  formed  during  a  test  drops  into  a  flask  beneath.  The 
test  should  be  carried  out  in  a  room  in  which  no  other  gas  is 
burnt,  and  the  air  of  which  is  not  otherwise  contaminated  with 
sulphur  dioxide. 

The  gas  is  burned  at  the  rate  of  0-5  to  07  cb.  ft.  per  hour, 
the  trumpet  tube  being  placed  on  the  burner  when  the  meter 

index  passes  a  point 
which  is  noted.  The 
products  of  combustion, 
together  with  the  am- 
monia evaporated  from 
the  carbonate,  pass 
through  the  condenser, 
where  the  sulphur  di- 
oxide is  condensed  from 
the  products  as  a  solu- 
tion of  ammonium  sul- 
phate, the  excess  of 
oxygen  present  effect- 
ing the  oxidation  of  the 
sulphite  to  sulphate.  As 
soon  as  the  required 
quantity  of  gas  has  been 
passed,  the  supply  is 
shut  off.  For  official 
purposes,  meters  are 
used  which  are  arranged 
to  cut  off  the  gas  supply 
automatically  when  10 
p1G  Io8t  cb.  ft.  have  passed,  and 

to    record    the   time   at 

which  this  takes  place.  For  unofficial  tests  this  is,  of  course, 
unnecessary.  After  cooling,  the  condenser  tube  and  cylinder 
are  washed  out  with  distilled  water  into  the  beaker  or  flask 
containing  the  condensed  liquid,  and  the  sulphur  in  the 
latter  determined  in  the  usual  way,  either  in  the  whole 
or  in  an  aliquot  part  of  the  solution,  by  precipitation  with 
barium  chloride.  From  the  weight  of  barium  sulphate  ob- 


TOTAL  SULPHUR  259 

tained,  in  grammes,  the  sulphur  in  grains  per  100  cb.  ft.  is 
readily  obtained  :  — 

r,    .  ,    f  g.  BaSO,  x  is.  AT.2  x  0.1374  x  100 

Grains  per  100  cb.  ft.  =  -  e  -  ^  -  ±^?  -  P'**      —  .  - 
gas  consumed  corrected  to  60  F.  and  30  in.  Bar. 

The  correction  of  the  gas  volume  to  60°  F.  and  30  in.  pressure 
is  effected  by  the  table  in  Lunge-Keane's  Technical  Methods 
vol.  ii.  pp.  690  to  691. 

This  method  tends  to  give  results  which  are  slightly  low 
owing  to  incomplete  oxidation  of  the  sulphites  to  sulphates, 
the  former  not  being  precipitated  by  barium  salts.  To  avoid 
this  possibility,  some  analysts  prefer  to  oxidise  the  solution 
with  bromine  water  before  precipitation,  whilst  others  oxidise 
with  nitric  acid,  and  precipitate  with  barium  nitrate  instead  of 
chloride.  J.  Fairley  (/.  Soc.  Chem.  Ind.,  1887,  p.  283)  dispenses 
with  the  use  of  ammonium  carbonate,  and  allows  a  solution  of 
hydrogen  peroxide  to  drip  down  the  condensing  cylinder  of  the 
Referees'  apparatus,  the  sulphur  being  then  obtained  in  the 
condensate  as  free  sulphuric  acid.  Instead  of  using  the 
gravimetric  method,  the  amount  of  sulphuric  acid  may  be  then 
determined  by  titration  with  normal  alkali,  provided  that  the 
hydrogen  peroxide  solution  used  is  neutral.  Or,  by  using  a 
known  volume  of  hydrogen  peroxide  solution  of  determined 
acidity,  the  sulphuric  acid  formed  may  be  found  by  deducting 
the  amount  of  the  latter  from  the  total  quantity  of  acid 
found. 

H.  Blair  (/.  Soc.  Chem.  Ind.,  1911,  p.  397)  has  proposed  the 
following  volumetric  method  for  the  estimation  of  the  sulphuric 
acid  obtained  by  the  Referees'  process.  An  aliquot  portion  of 
the  solution  is  boiled  to  volatilise  the  ammonium  carbonate, 
thus  leaving  neutral  ammonium  sulphate  ;  an  excess  of  neutral 
formaldehyde  solution  (about  30  per  cent.)  is  then  added  to  the 
hot  solution,  which  combines  with  the  ammonia,  forming  hexa- 
methylene  tetramine,  and  liberates  sulphuric  acid,  in  accordance 
with  the  equation  : 

2(NH4)2SO4  +  6CH2O  =  N4(CH2)6  +  2H2SO4 


The  liberated  sulphuric  acid  is  then  determined  by  titration 
with  decinormal  alkali,  using  phenolphthalein  as  indicator  ;  I  c.c. 
A"/  10  alkali  =  0-0247  g.  S. 


260 


TECHNICAL  GAS-ANALYSIS 


F.  Fischer  used  for  this  determination  the  following  apparatus, 
shown  in  Fig.  109,  in  one-tenth  actual  size.  The  gas  supply, 
after  passing  the  experimental  meter,  is  burnt  in  the  small 
Bunsen  burner  B,  at  the  bottom  of  the  adapter  C  ;  the  latter  is 
fitted  into  the  bulb  n,  at  v,  either  by  a  cork  or  by  an  asbestos 
ring.  The  tube  is  surrounded  by  a  condenser  K,  the  water 
supply  of  which  enters  at  a  and  leaves  at  w.  The  water  formed 
in  the  combustion  condenses  in  the  tube  n,  n, 
and  there  absorbs  the  sulphurous  and  sulphuric 
acids,  the  liquid  products  being  finally  collected 
in  F.  The  sulphur  content  is  determined  by 
titration  with  decinormal  alkali,  after  first 
oxidising  the  sulphurous  acid  with  potassium 
permanganate  ;  or  a  test-tube,  containing  liquor 
ammoniae  may  be  placed  by  the  side  of  the 
burner  during  the  combustion,  in  order  to 
ensure  a  more  complete  condensation  of  the 
SO2,  and  the  sulphuric  acid  tested  gravimetri- 
cally.  The  current  of  gas  is  regulated  so  that 
there  is  an  excess  of  4-6  per  cent,  of  free  oxygen, 
as  can  be  determined  by  taking  a  sample  of 
the  exit  gases  at  o ;  with  good  condensation, 
about  50  c.c.  of  liquid  are  collected  per  50  litres 
of  gas  burnt. 

In  Germany  the  method  mostly  used  for  the 
determination  of  total  sulphur  in  gas  is  that 
of  Drehschmidt,  described  in  Post's  Chemisch- 
technische  Analyse,  1888,  which  we  render  here 
according  to  the  description  by  Pfeiffer  in 
Lunge-BerFs  Chemisch-technische  Untersuchungsmethoden,  vol. 
iii.  p.  294.  This  process,  similar  to  those  previously  described 
by  Evans  and  Poleck,  is  founded  on  the  oxidation  of  the 
combustion  products  by  brominated  potassium  carbonate 
solution,  and  has  been  found  in  prolonged  use  as  the  best  in 
existence. 

Fig.  no  shows  the  apparatus  used  for  this  process.  The 
gas  is  first  passed  through  an  experimental  gas-meter,  and  then 
to  the  Bunsen  burner  fixed  gas-tight  in  the  case  A.  The  burner 
is  closed  with  a  cap  of  wire  gauze,  to  prevent  the  flame  from 
striking  back ;  for  the  purpose  of  regulating  the  air  supply  it  is 


FIG.  109. 


TOTAL  SULPHUR  261 

fitted  with  a  movable  casing,  adjusted  in  such  manner  that  the 
flame  is  just  rendered  non-luminous.  Case  A  consists  of  two 
parts,  fitting  into  each  other,  one  placed  over  the  other,  with  a 
tight,  conical  joint.  Into  the  lower  part  enter  the  ends  of  a 
forked  tube  b  for  admitting  the  air  required  for  combustion. 


FIG.  no. 

This  air  enters  from  below  into  the  tower  B,  filled  with  bits  of 
pumice,  where  it  is  purified  from  any  sulphur  compounds  con- 
tained in  it  by  caustic  potash  solution  dropping  down  from  the 
funnel  tube  at  the  top,  and  is  then  carried  by  the  rubber  tube  b 
to  the  burner.  The  upper  part  of  A,  through  which  the  burner 
passes,  carries  a  circular  pocket,  filled  with  mercury,  forming  a 
gas-tight  joint  with  the  glass  cylinder  C.  From  this  a  glass  tube, 


262  TECHNICAL  GAS-ANALYSIS 

fused  to  C,  carries  the  gases  to  the  first  of  the  absorption  bottles 
DD,  into  which  it  enters  by  a  ground-in  stopper.  The  last  of 
these  bottles  is  connected  with  a  water-jet  pump.  Each  of  the 
cylinders  is  charged  with  a  5  per  cent,  potassium  carbonate 
solution ;  the  first  two  cylinders,  moreover,  receive  a  few  drops 
of  bromine,  in  order  to  oxidise  the  sulphurous  into  sulphuric 
acid. 

Having  regard  to  the  slight  movability  of  the  various  con- 
nections, the  apparatus  is  mounted  in  such  manner  that  in 
making  the  connections  no  force  need  be  applied.  In  the  first 
instance  cylinder  C  is  fixed  on  the  metal  stand  E  by  means  of 
the  metallic  clamp,  and  is  connected  with  the  first  absorbing 
bottle  D  by  the  ground-in  joint.  Case  A  is  lowered  so  far 
that  it  can  be  turned,  together  with  the  burner,  sideways  away 
from  C,  so  that  the  flame  can  be  lighted.  The  flame  is 
regulated  for  a  consumption  of  from  20  to  30  litres  per  hour, 
the  water-jet  pump  is  started,  and  case  A  with  the  burner  is 
brought  back  into  the  position  shown  in  the  drawing,  as  soon  as 
the  index  of  the  meter  passes  through  the  point  D.  Sometimes 
the  flame  must  be  regulated  again  ;  it  ought  to  show  a  sharp 
outline.  Each  estimation  of  the  sulphur  requires  about  50 
litres  of  gas. 

After  the  test  is  finished,  the  various  parts  of  the  apparatus 
are  taken  out  in  the  inverted  order,  compared  to  that  in  which 
they  were  put  together.  The  cylinder  C  and  the  absorption 
bottles  DD  are  washed  out  into  a  beaker,  the  liquid  is  acidu- 
lated with  hydrochloric  acid,  boiled  up  to  driving  out  all  bromine, 
and  dilute  hot  barium  chloride  solution  is  added.  One  g.  BaSO4 
formed  indicates  0-1373  g.  S. 

Contrary  to  Hempel  (GasanaL  Methoden^  3rd  ed.,  p.  256) 
Pfeiffer  maintains  that  Drehschmidt's  apparatus  is  nothing  like 
so  easily  breakable  as  it  would  appear.  But,  after  comparative 
trials,  he  employs  only  the  principal  parts  of  it,  viz.,  the  case  A 
with  the  burner  and  cylinder  C.  These  are  placed  on  a  table, 
the  cylinder  C  being  loosely  held  by  an  ordinary  stand,  and 
connected  with  the  wash-bottle  shown  in  Fig.  1 1 1  (without  the 
elbow  pipe  shown  there),  in  such  manner  that  its  delivery  pipe 
passes  through  the  wide  entrance  tube  of  the  bottle,  the  joint 
being  made  gas-tight  by  means  of  a  piece  of  rubber  tubing. 
Through  the  second  bore  in  the  stopper  of  the  wash-bottle 


TOTAL  SULPHUR  263 

passes  the  narrowed  end  of  a  calcium  chloride  tube,  holding 
about  ioo  c.c.,  and  half  filled  with  bits  of  glass.  This  simple 
absorbing  contrivance  is  charged  with  a  little  water  and  25  c.c. 
of  decinormal  caustic  soda  solution,  poured  in  through  the 
calcium  chloride  tube,  so  that  the  bits  of  glass  are  equally 
moistened  with  it.  Then  I  c.c.  of  pure  hydrogen  peroxide 
(Merck's  "  perhydrol,"  containing  30  per  cent.  H2O2)  is  added, 
and  the  free  end  of  the  calcium  chloride  tube  is  connected  with 
a  tube  leading  to  the  water-jet  aspirator.  Pfeiffer  also  employs 
a  different  arrangement  for  washing  the  air  serving  for  combus- 
tion, viz.,  a  i -litre  WoulfFs  bottle  with  two  necks, 
through  one  of  which  passes  a  tube  with  its  bottom 
cut  off  in  a  slanting  way,  just  dipping  into  the 
strong  caustic  soda  solution  contained  in  the  bottle ; 
through  the  other  neck  passes  a  wide  absorption- 
tube,  holding  about  200  c.c.,  and  loosely  rilled 
with  wood-cellulose.  Before  the  test  the  Woulff's 
bottle  is  inclined  in  such  a  way  that,  by  blowing 
through  a  rubber  tube  into  the  free  end  of  the 
dipping-in  tube,  the  caustic  liquor  is  driven  up 
in  the  absorption -tube  and  moistens  the  wood- 
cellulose.  Then  the  free  end  of  this  tube  is 
connected  with  the  air-conduit  b  of  Drehschmidt's 
apparatus.  Apart  from  this  the  test  is  carried 
out  as  described,  but  it  is  preferable  to  place  the  wash-bottle  in 
a  tin  pot  filled  with  water,  in  order  to  prevent  a  too  early 
decomposition  of  the  hydrogen  peroxide. 

After  finishing  the  passage  of  the  gas,  the  absorbing  liquid 
is  washed  from  the  calcium  chloride  tube  back  into  the  wash- 
bottle,  adding  in  the  end  a  drop  of  dimethylamidoazobenzol 
(methyl  orange)  as  indicator,  and  the  excess  of  caustic  alkali  is 
retitrated  with  decinormal  acid.  Each  cubic  centimetre  of 
N/io  alkali  used  is  equivalent  to  0-001603  g.  or  0-02478  grain  of 
sulphur,  and  the  number  of  grains  of  sulphur  per  ioo  cb.  ft. 
is  obtained  by  the  equation  : — 

Grains  per  ioo  cb.  ft.  = 

Number  of  cubic  centimetres  of  JV/io  NaOH  x  0-02478  x  ioo 
Gas  consumed  corrected  to  10  N.T.P. 

The  exactness  of  this  volumetrical  method  is  proved  by  the 


264  TECHNICAL  GAS-ANALYSIS 

fact  that  in  the  combustion  no  notable  quantity  of  nitric  acid  is 
formed,  that  no  more  sulphuric  acid  is  absorbed  in  a  second 
receiver,  and  that  the  results  of  titration  exactly  coincide  with 
the  gravimetrical  estimation. 

The  apparatus  of  Somerville  (/.  Gas  Lighting,  1910,  p.  29) 
resembles  that  of  Drehschmidt.  The  gas  is  burnt  at  the  rate 
of  about  \  cb.  ft.  per  hour,  and  the  products  of  combustion  are 
aspirated  through  a  wash-bottle  containing  100  c.c.  of  N/iooo 
iodine  solution  and  a  few  cubic  centimetres  of  starch  solution. 
The  gas  is  passed  through  till  the  solution  is  just  decolorised, 
when  the  gas  meter  is  at  once  by-passed.  The  iodine  solution 
employed  contains  0-1268  g.  I,  equivalent  to  00016  g.  or 
0-024688  grains  of  sulphur,  which  is,  therefore,  the  amount 
present  in  the  volume  of  gas  burned. 

Various  other  methods  have  been  described  for  this  purpose, 
of  which  we  mention  those  following  : — 

Dickert  (/.  Gasbeleucht.,  1911,  p.  182)  employs  an  alkaline 
solution  of  "perhydrol"  (hydrogen  peroxide),  which  oxidises 
the  sulphur  compounds  in  the  cold  to  sulphuric  acid,  to  be 
determined  as  barium  sulphate.  Bosshard  and  Horst  (ibid., 
1912,  p.  1093)  declare  this  method  to  be  quite  inaccurate. 

Niemeyer  (/.  Gasbeleucht.,  1911,  p.  1078;  Chem.  Zentralb., 
1912,  ii.  p.  375)  estimates  the  sulphur  dioxide  iodometrically  in 
the  combustion  products  of  the  gas,  and  adds  6  to  8  per  cent,  to 
the  value  of  sulphur  thus  found,  to  allow  for  the  other  sulphur 
compounds  in  coal-gas  [that  is  surely  too  "  rough  and  ready  "  !]. 

McBride  and  Weaver  (/.  Ind.  and  Eng.  Chem.,  1913,  p.  474) 
made  a  comparison  of  the  Gas  Referees'  apparatus  (supra, 
p.  257)  with  the  modifications  proposed  by  Hinman-Jenkins 
and  by  Elliott,  with  the  result  that  any  of  these  apparatus  is 
capable  of  giving  satisfactory  results  if  properly  worked. 

The  same  authors  (ibid.,  p.  598,  and  /.  Gas  Lighting,  1913, 
pp.  531  and  598)  compare  the  gravimetric,  volumetric,  and 
turbidimetric  methods  for  determining  the  sulphate  present  in 
solutions  obtained  in  the  Gas  Referees'  apparatus.  For 
accurate  work  they  prefer  the  gravimetric  methods  (precipita- 
tion with  barium  chloride).  For  rapid  work  the  "  turbidimeter  " 
can  be  employed.  This  is  a  portable  apparatus  consisting  of 
a  glass  cylinder,  graduated  in  cubic  centimetres,  held  in  place 
above  a  16  candle-power  carbon  filament  lamp.  The. solution 


HYDROGEN  265 

from  the  sulphur  apparatus  is  neutralised  with  hydrochloric 
acid,  and  an  additional  2  c.c.  of  acid  (i  :  i)  is  added.  The 
volume  is  measured,  and  90  c.c.  taken  for  the  test ;  10  c.c.  of 
10  per  cent,  barium  chloride  solution  are  added  to  the  solution, 
which  should  be  at  25°  to  30°  C.,  and  the  whole  stirred  for  one 
minute.  The  suspension  is  poured  gradually  into  the  turbid- 
imeter  until  the  filament  of  the  lamp  cannot  be  seen  ;  it  is  then 
poured  back,  and  the  turbidity  again  tested  until  the  point  is 
fixed  within  i  mm.  The  amount  of  sulphur  is  then  ascertained 
from  tables  of  curves  obtained  previously. 

This  method,  according  to  the  authors,  is  accurate  to  within 
2  or  3  per  cent,  of  the  quantity  of  sulphur  present.  But  a  critic 
in  the  J.  Gasbeleucht^  1913,  p.  919,  justly  remarks  that  that 
method  is  necessarily  inaccurate,  and  has  no  advantage  over 
the  direct  titration  of  the  acids  formed  in  burning  the  gas  and 
absorbed  by  a  neutralised  hydrogen  peroxide  solution. 

HYDROGEN. 

As  a  qualitative  proof  for  the  presence  of  hydrogen  Phillips 
(Amer.  Chem.  /.,  1894,  p.  259)  employs  dry  palladious  chloride, 
which  with  hydrogen  forms  hydrogen  chloride,  to  be  proved  by 
the  precipitation  of  silver  chloride  when  afterwards  passing  the 
gases  through  a  solution  of  silver  nitrate.  This  reagent  is  not 
applicable  in  the  presence  of  olefms  and  of  carbon  monoxide, 
which  equally  act  on  palladium  chloride. 

Zenghelis  (Z.  anal.  Chem.,  1910,  p.  729),  to  prove  the 
presence  of  hydrogen  in  presence  of  methane,  ethylene, 
acetylene,  etc.,  passes  the  gas  mixture  through  a  solution  of 
sodium  hydroxide  and  then  through  a  tube  containing  platinum 
foil  or  wire  gauze,  previously  ignited,  and  immersed  in  a  few 
cubic  centimetres  of  a  warm  solution  of  sodium  molybdate  (i  g. 
MoO3  dissolved  in  caustic  soda  solution  and  diluted  to  200  c.c.). 
The  hydrogen  is  occluded  by  the  platinum  and  immediately 
reduces  the  molybdate,  imparting  to  it  an  intense  blue  colour. 
If  the  amount  of  hydrogen  is  small  or  the  test  solution  is  old, 
the  colour  is  a  light  greenish  blue.  Palladium  acts  even  more 
delicately  than  platinum.  Arsine,  phosphine,  and  carbon 
monoxide  must  be  removed  before  applying  the  test. 

Pereira  (/.  Amer.  Chem.  Soc.  Abstr.,  1913,  p.  3284)  detects 


266  TECHNICAL  GAS-ANALYSIS 

hydrogen  by  means  of  its  reducing  action  (production  of  a  blue 
coloration)  on  solutions  of  phosphomolybdic  and  sodium 
tungstate  in  the  presence  of  palladium  chloride  as  a  catalyst. 

The  physical  method,  worked  out  by  Haber  and  Lowe  by 
the  help  of  their  "interferometer"  (Z.  angew.  Chem.,  1910, 
P-  X393  ;  vide  supra,  p.  177)  can  be  also  used  in  this  case. 

Quantitative  Estimation  of  Hydrogen.  —  Hydrogen  is 
practically  always  determined  by  combustion  with  oxygen, 
either  by  means  of  explosion  or  by  the  catalytic  action  of 
heated  palladium  or  platinum.  We  have  frequently  had 
occasion  to  describe  this  operation  in  former  chapters,  e.g. 
pp.  71,  90,  97,  109,  129,  152,  156,  160,  162,  167,  174,  where 
also  the  (generally  occurring)  cases  are  treated  in  which  other 
combustible  gases  are  present  at  the  same  time. 

The  determination  of  hydrogen  by  absorption  in  palladium 
hydrosol  has  been  described  supra,  p.  131. 

Holm  and  Kutzbach  (Z.  fiir  chem.  Apparatenkunde,  1905, 
p.  130)  describe  an  apparatus  for  estimating  hydrogen  by  its 
strong  conductivity  for  heat,  principally  intended  for  a  con- 
tinuous estimation  of  that  gas  in  water-gas,  coal-gas,  or 
producer-gas.  It  does  not  appear  to  have  found  much  practical 
application. 

Schultze  and  Koepsel  (Braunkohle,  1913,  p.  740;  Z.  angew. 
Chem.,  1913,  Ref.y  p.  466)  describe  a  method  for  the  uninterrupted 
estimation  of  hydrogen  in  producer-gas,  founded  on  passing 
the  gas  over  electrically  heated  wire  and  measuring  the 
difference  of  conductivity. 

The  estimation  of  hydrogen  in  the  presence  of  methane 
will  be  described  later  on,  when  treating  of  methane. 

The  apparatus  of  Dosch,  mentioned  supra,  p.  230,  may  be 
utilised  for  the  continuous  estimation  of  hydrogen  in  producer- 
gases. 

METHANE. 

Methane  (marsh-gas)  cannot  be  estimated  by  absorption 
methods,  as  there  are  no  suitable  absorbents  for  it.  It  is 
always  estimated  by  combustion  ;  in  the  presence  of  hydrogen 
"fractional  combustion"  (pp.  71,  164,  and  169) can  be  applied,  as 
methane  is  not  as  easily  combustible  as  hydrogen,  and  remains 
unchanged  at  temperatures  at  which  hydrogen  as  well  as  other 


METHANE  267 

hydrocarbons  are  burnt.  When  only  hydrogen  has  to  be 
taken  into  account  (e.g.  where  there  are  no  heavy  hydrocarbons 
present,  or  when  these  have  been  removed  by  absorbents), 
both  hydrogen  and  methane  can  be  burnt  together,  and  the 
proportion  of  methane  ascertained  by  estimating  that  of  the 
carbon  dioxide  formed,  whose  volume  is  equal  to  that  of  the 
methane  burned ;  the  volume  of  oxygen  required  is  twice  that 
of  the  methane : 

CH4  +  2O2  =   CO.2  +  2H2O. 

2  vols.        4  vols.         2  vols.          0  vol. 

Methane  is  the  principal  dangerous  constituent  of  the  air 
of  coal-pits,  when  rendered  explosive  by  the  presence  of 
"fire-damp""  ("grisou"  in  French).  Hence  Coquillion,  when 


FIG.  112. 

describing  his  apparatus  for  examining  the  air  of  coal-pits, 
called  it  "  Grisoumeter?  and  this  name  has  also  been  given  to 
various  other  apparatus  proposed  for  the  same  purpose.  The 
principle  of  Coquillion's  apparatus  (Comptes  rend.,  1877,  clxxxiv. 
p.  458)  is  the  burning  of  a  mixture  of  methane  and  air,  without 
explosion,  by  contact  with  heated  platinum  or  palladium,  and 
noting  the  contraction  produced. 

Coquillion's   grisoumeter   is    shown    in    Fig.    112.     A    is  a 


268 


TECHNICAL  GAS-ANALYSIS 


measuring-tube,  ending  at  the  top  in  a  "f-piece  with  a  glass 
tap  on  each  side.  The  tube  contains  from  these  taps  down 
to  the  zero  mark  near  the  bottom,  25  c.c.,  but  the  upper,  wider 
part  is  not  divided,  the  lower,  narrower  part  being  divided  in 
tenths  of  a  cubic  centimetre.  The  bottom  of  this  tube  is 
connected  by  a  rubber  pipe  with  the  levelling-bottle  F,  by 
means  of  which  A  is  filled  and  emptied,  like  Orsat's  apparatus 


FIG.  113. 

(p.  66).  By  means  of  the  two  top  taps,  burette  A  can  be 
connected  either  with  the  reservoir  containing  the  gas  to  be 
tested,  or  with  the  combustion-vessel  B,  which  is  hydraulically 
sealed  by  the  cylinder  C'.  If,  after  combustion,  the  carbon 
dioxide  formed  is  to  be  removed  from  the  gas  and  measured, 
the  apparatus  is  provided  with  an  absorbing- vessel  D  (Fig.  113) 
containing  caustic  potash  solution ;  this  shape  was  called  by 
Coquillion  "  Carburometre."  Here,  between  the  gas-burette 
A  and  the  combustion-vessel  B,  is  interposed  a  glass  vessel  D, 
containing  caustic  potash  solution.  The  vessel  B  is  closed  by 
a  rubber  cork,  through  which  pass  two  brass  pins,  provided  cm 
the  outside  with  screw  clamps  for  receiving  the  wires  from  an 
electric  battery,  and  connected  inside  B  by  a  spiral  of  thin 


METHANE  269 

platinum  or  palladium  wire  which  becomes  red  hot  when  an 
electric  current  is  passed  through. 

This  apparatus  is  manipulated  as  follows : — A  is  filled  with 
water  by  raising  F ;  connection  is  made  with  the  outside 
cylinder  containing  the  sample  of  gas ;  the  latter  is  opened 
under  water  by  removing  its  cork,  and  by  lowering  F  the  gas 
is  transferred  into  A,  where  it  is  drawn  in  as  far  as  the  zero 
mark  in  the  usual  manner.  Now  the  current  is  closed  and 
the  gas  is  passed  over  the  red-hot  platinum  spiral  in  B  by 
raising  the  levelling-bottle  F,  making  it  go  backwards  and 
forwards  several  times.  After  cooling,  the  contraction  is  noted, 
half  of  which  corresponds  to  the  methane.  If  there  is  too 
little  oxygen  present,  more  air  (measured)  must  be  admitted, 
and  the  passage  over  the  red-hot  platinum  repeated. 

The  combustion  takes  place  easily  and  rapidly,  but  the 
cooling  takes  a  long  time,  and  the  results  are  only  approximate. 
Small  percentages  of  methane  in  the  air  cannot  be  estimated 
by  this  instrument. 

The  principle  on  which  Coquillion's  grisoumeter  is  founded 
has  been  applied  by  quite  a  number  of  chemists  by  means  of 
other  apparatus.  We  now  describe  the  apparatus  constructed 
by  Cl.  Winkler  (Z.  anal.  Chem.,  1889,  p.  286).  He  employed 
a  Hempel's  tubulated  gas-pipette,  as  shown  in  Fig.  114.  Into 
this  pipette  two  brass  electrodes  are  introduced,  175  mm.  long, 
5  mm.  thick,  not  varnished.  At  the  bottom  they  have  holes 
for  the  current  wires  ;  at  the  top,  incisions  in  which  the  two 
ends  of  a  platinum  spiral  wire  fixed  by  small  screws.  This 
spiral  consists  of  platinum  wire  0-35  mm.  thick,  made  by 
coiling  the  wire  over  a  steel  pin  1-3  mm.  thick,  and  leaving  at 
the  ends  I  cm.  for  fixing  it  in  the  above-mentioned  incisions. 
Before  doing  so,  the  electrodes  are  passed  through  a  twice- 
perforated  cork  (not  shown  in  the  drawing),  which  reaches 
half-way  up  and  prevents  them  from  moving.  These  electrodes 
must  be  2  or  2-5  cm.  distant  from  the  top  of  the  pipette,  which 
is  completely  filled  with  water  and  kept  closed  in  the  usual 
manner.  This  apparatus  is  manipulated  in  the  following 
manner : — The  gas,  previously  freed  from  absorbable  con- 
stituents and  (by  "fractional  combustion,"  pp.  71,  164,  169)  from 
hydrogen,  and  thus  containing  only  methane  and  nitrogen, 
is  measured  in  a  Hempel's  burette  and  mixed  with  a  measured 


270 


TECHNICAL  GAS-ANALYSIS 


excess  of  air.  This  burette  is  connected  by  an  ordinary  glass 
capillary  with  the  pipette,  Fig.  1 14,  and  the  current  closed.  Now 
the  levelling-tube  of  the  burette  is  lifted  up  with  the  left  hand,  one 
of  the  pinchcocks  is  opened  entirely,  the  other  one  partly  with 
the  right  hand,  and  thus  the  gas  is  slowly  transferred  into  the 
pipette.  As  soon  as  the  water-level  has  sunk  below  the 

platinum  spiral,  this  becomes 
red  hot.  Now  the  entrance  of 
the  gas  must  be  interrupted  for 
a  moment  and  the  remainder  of 
the  gas  introduced  very  grad- 
ually, by  which  proceeding  the 
combustion  is  made  to  take 
place  quietly  and  without  any 
risk  of  an  explosion.  If,  how- 
ever, the  gas  is  passed  in  too 
quickly,  or  if  it  is  first  intro- 
duced into  the  pipette  and  the 
current  is  then  closed,  an  ex- 
plosion may  take  place  which 
throws  out  the  stopper  contain- 
ing the  electrodes,  and  the  water 
out  of  the  side-bulb.  The  thick- 
ness of  the  wire  and  the  number 
of  coils  must  correspond  to  the  strength  of  the  current.  The 
above-mentioned  dimensions  refer  to  a  current  from  two  small 
Grove  elements.  If  the  wire  is  too  thin,  it  fuses ;  if  it  is  too 
thick,  it  does  not  get  hot  enough,  but  it  is  not  difficult  to  hit 
the  proper  proportions.  The  combustion  is  finished  within 
one  minute.  Now  the  current  is  shut  off,  the  pipette  (the 
upper  part  of  which  gets  rather  hot)  is  allowed  to  cool  down, 
the  gas  is  retransferred  into  the  burette,  the  carbon  dioxide 
is  removed  by  means  of  a  caustic  potash  pipette,  and  the  total 
contraction  noted.  By  dividing  the  latter  by  3  the  volume 
of  the  methane  is  found. 

Dennis  and  Hopkins  (Z.  anorg.  Chem.,  1899,  xix.  p.  179) 
modify  Winkler's  apparatus  by  filling  the  pipette  with  mercury 
and  slightly  modifying  the  electrodes. 

Winkler's  process  can  be  applied  to  the  estimation  of 
methane  in  natural  heating  gas,  in  "  blowers "  of  coal-pits,  in 


Jr'iG.  114. 


METHANE  271 

marsh-gas,  producer-gas,  etc.  First  remove  by  absorption 
successively,  carbon  dioxide,  heavy  hydrocarbons,  oxygen,  and 
carbon  monoxide,  by  the  methods  indicated  supra  in  several 
places  (e.g.,  p.  64  and  152),  then  hydrogen  by  combustion  with 
air  and  palladium  asbestos  (p.  164),  and  now  burn  the  methane 
as  just  described. 

Leonard  A.  Levy(/.  Soc.  Chem.  Ind.,  1912,  p.  1153)  describes 
a  new  apparatus  for  the  examination  of  the  air  of  coal-pits, 
for  estimating  methane,  carbon  dioxide,  and  oxygen.  The 
methane  is  burned  in  a  silicon  capillary  (0-5  to  i  mm.  inside 
diameter)  of  appropriate  form,  in  which  a  platinum  wire  can 
be  heated  to  a  white  heat  by  the  electric  current.  Owing  to 
the  narrow  inside  space,  the  gas  is  prevented  from  passing 
too  quickly  through  it,  and  complete  combustion  is  assured. 
The  apparatus  is  made  in  two  modifications,  one  of  which 
serves  only  for  a  rapid  estimation  of  methane,  the  other  for 
methane,  CO2,  and  O.  Both  are  sold  by  Alexander  Wright 
&  Co.,  Ltd.,  Westminster. 

Other  "  Grisoumeters "  have  been  constructed  by  a  number 
of  chemists  as  follows  : — 

Mertens  (Z.  anal.  Chem.,  1887,  p.  42). 

Thorner  (Z.  angew.  Chem.,  1889,  p.  642). 

Jeller  (Z.  angew.  Chem.,  1896,  p.  692). 

Burell  (/.  Ind.  Eng.  Chem.,  iv.  p.  96). 

Wendriner  (ibid.,  1902,  p.  1062). 

Rosen  (Ger.  P.  245367). 

Akkumulatorenfabrik,  Berlin  (Ger.  Ps.  268736,  268737, 
268844,  268845,  269131). 

Kraushaar  (Ger.  P.  268898). 

Beckmann  (Ger.  P.  268963). 

The  combustion  of  methane  by  explosion  has  been  described 
supra,  pp.  156  and  171. 

A  special  treatise  on  the  analysis  of  coal-pit  gases  has  been 
written  by  O.  Brunck  (Chemische  Untersuchung  der  Grubenwetter, 
Freiberg,  1900). 

A  qualitative  reaction  on  methane,  according  to  Hauser 
and  Herzfeld  (Ber.,  1912,  p.  3515),  is  afforded  By  the  action  of 
ozonised  oxygen,  whereby  formaldehyde  is  formed,  which  is 
recognised  by  its  smell,  or  by  the  action  of  morphine-sulphuric 
acid  (Mannich,  Arb.  Pharmaz.  Inst.,  Berlin,  1906,  p.  227). 


272  TECHNICAL  GAS-ANALYSIS 

Hauser  (Anal.  fis.  quim.,  1913,  p.  280;  Chem.  Soc.  Abstr., 
I9I3>  P-  72°)  points  out  that  in  the  analysis  of  combustible 
gases  by  explosion  an  appreciable  error  is  caused  by  the 
combustion  of  nitrogen,  but  the  presence  of  8-33  per  cent,  of 
methane  ensures  that  the  combustion  of  N  is  inappreciable. 

Cl.  Winkled s  Method  of  Examining  Coal-pit  Air  containing 
Very  Small  Quantities  of  Methane. — It  is  frequently  assumed  that 
the  prevention  of  danger  from  fire-damp  in  coal-pits  need  only 
extend  to  ascertaining  whether  the  atmosphere  of  the  pit 
contains  enough  methane  to  make  it  inflammable  or  explosive, 
various  apparatus  for  which  has  been  described  above. 
This  is,  however,  a  mistake.  The  mining  engineer  must  try  to 
prevent  any  accumulation  of  fire-damp  before  the  percentage  of 
methane  has  reached  the  lower  limit  of  explosiveness.  By  the 
examination  for  methane,  both  in  the  branch  current  and  in 
the  principal  current  of  air  issuing  from  the  pit,  he  must 
carefully  establish  the  average  composition  of  the  pit-air,  as  it 
changes  with  the  progress  of  working  the  coal-seams.  In  all 
such  cases  it  is  necessary  to  determine  comparatively  small 
quantities  of  methane,  such  as  cannot  possibly  be  read  off  in  a 
gas-burette  with  any  degree  of  exactness.  The  following 
process,  however,  attains  the  desired  end  in  a  simple  manner. 
It  consists  in  burning  the  methane  contained  in  a  large  volume 
of  pit-air  by  means  of  electrically  glowing  platinum,  and  then 
estimating  the  carbon  dioxide  formed  by  titration.  This 
process  has  been  thoroughly  tested  in  the  Freiberg  Mining 
Academy,  and  it  has  been  established  there  that  a  stream  of 
induction  sparks,  even  of  considerable  length,  cannot  replace 
the  electrically  glowing  platinum. 

All  the  operations  of  measuring,  burning,  and  titrating  are 
carried  out  in  the  conical  flask  A,  Fig.  115,  which  during  the 
combustion  is  turned  upside  down,  as  shown  in  the  figure.  On 
its  neck  it  has  a  circular  mark,  up  to  which  it  is  ordinarily 
closed  by  a  twice-perforated  rubber  cork,  with  glass  rod 
stoppers.  The  contents  of  the  flask  up  to  this  mark  are 
ascertained  by  weighing  or  measuring,  and  are  marked  on 
the  glass  by  etching ;  it  should  generally  hold  about  2  litres, 
but  in  the  case  of  gases  containing  much  methane,  I  litre  is 
enough. 

When  the  flask  has  to  serve  for  a  combustion  of  the  gas 


METHANE 


273 


contained  in  it,  its  stopper  is  taken  out  under  water  and 
replaced  by  a  rubber  cork  /£,  with  electrodes  e.  A  second 
perforation,  otherwise  closed  by  a  glass  rod,  serves  for  intro- 
ducing by  means  of  a  pipette  a  certain  volume  of  water,  say 


FIG.  115. 

10  c.c.  This  water  during  the  combustion  prevents  the  contact 
of  the  gas  with  the  rubber,  which  might  produce  considerable 
errors ;  when  turning  the  flask  upside  down,  it  forms  the 
protecting  layer  w.  Its  volume  must  be  known,  as  well  as  that 
of  the  electrode  e,  and  these  amounts  must  be  deducted  from 
the  contents  of  flask  A. 

S 


274 


TECHNICAL  GAS-ANALYSIS 


Lest  this  flask  should  get  hot  during  the  combustion,  it  is 
immersed  in   the  water-filled    beaker  B,  and   prevented  from 
rising  up  by  the  adjustable  holder  H,  as  shown  in  the  figure. 
If  instead  of  a  glass  beaker,  a  tin  vessel  is  employed, 
that  holder  can   be  fixed  to  its  side.     The  wires  d 
and  dv  which  transmit  the  electrical  current,  should 
be  at  least    I    mm.   thick   and   insulated   by  gutta- 
percha. 

The  electrode  e,  shown  half-size  in  Fig.  116,  has 
been  constructed  by  O.  Brunck.1  It  is  made  of  brass 
and  must  not  be  varnished,  to  avoid  any  organic 
substances.  Its  parallel  arms  a  and  alt  at  the  top 
form  an  open  ring  b,  which  carries,  by  means  of 
screws,  the  platinum  spiral  c,  and  at  the  same  time 
protects  this  against  shocks.  In  their  lower  part  the 
arms  are  insulated  by  a  strong  strip  of  india-rubber, 
and  at  the  bottom  they  are  continued  into  a  cylin- 
drical part  d,  passing  gas-tight  through  the  central 
opening  of  the  cork  of  flask  A,  so  that  the  insulating 
rubber  strip  does  not  project  above  the  protecting 
layer  of  water  w  (Fig.  115).  This  insulating  strip 
is  continued  downwards  to  the  end,  being  thinner 
there ;  at  the  bottom  the  holes  e  and  e^  are  drilled 
into  the  two  arms  ;  into  these  holes  the  current 
wires  are  introduced  and  held  fast  by  screws  /  and 
fv  The  spiral  e  consists  of  platinum  wire,  0-35  mm. 
thick ;  the  total  length  of  wire  within  the  screw 
clamps  is  7  cm.  In  order  to  heat  this  platinum 
spiral  bright  red,  without  any  fear  of  fusing  it,  a 
current  of  8  or  9  amperes  should  be  applied,  e.g., 
by  two  large  Bunsen  elements  placed  in  series,  or 
*  KI  by  two  storage-cells. 

Manipulation. — Flask  A  is  filled  with  distilled 
water  carried  into  the  coal-pit,  and  the  water  run  out  on  the 
spot  where  the  sample  of  gas  is  to  be  taken.  The  flask  is  closed 
by  its  twice  perforated  cork,  and  taken  into  the  laboratory. 
If  the  sample  had  been  taken  in  another  vessel,  e.g.,  the  zinc 
cylinder  shown  in  Fig.  14,  p.  16,  flask  A  is  filled  from  this  in 


1  It  is  sold  by  Louis  Jentzsch,  Silbermannstrasse  I,  Freiberg,  in  Saxony. 


METHANE  275 

the  laboratory,  taking  care  to  let  the  inlet-tube  end  at  the 
highest  point  of  the  flask,  previously  filled  with  water  and 
inverted  under  water,  so  that  the  gas  comes  into  the  least 
possible  contact  with  the  water. 

After  filling  the  flask  A  with  the  gas  to  be  examined,  it  is 
closed  by  the  other  rubber  cork,  provided  with  the  electrode  e, 
the  exchange  of  corks  being  effected  under  water  of  the 
temperature  of  the  room.  The  protecting-water  w  is  put  in, 
the  current  wires  d  and  d±  are  attached,  A  is  placed  in  the 
water  contained  in  B,  and  fixed  by  the  holder  H.  Now  the 
current  is  closed  and  the  platinum  spiral  kept  at  a  bright  red 
heat  for  half  an  hour,  in  order  to  burn  the  methane  completely 
by  the  oxygen,  which  is  always  present  in  excess  in  such  cases. 
Then  the  current  is  interrupted,  the  electrode  cork  is  replaced 
by  the  ordinary  cork,  and  the  carbon  dioxide  is  titrated  by 
baryta  water,  as  described  on  pp.  136,  142,  and  223.  As  a  rule, 
the  baryta  water  can  be  run  in  from  the  burette  without  taking 
out  the  cork.  The  volume  of  gas  employed  must  be  reduced 
to  normal  conditions  (o°  or  15°  and  760  mm.). 

Heavy  hydrocarbons  and  carbon  monoxide  should  not  be 
present  in  the  gas.  Carbon  dioxide  is  generally  present;  it 
must  be  estimated  in  another  sample  of  gas,  e.g.,  by  the  method 
of  Hesse,  p.  135,  and  deducted  from  the  total  CO2  found  after 
combustion. 

Example — 
Contents  of  absorbing  bottle        .  .  .  .  .      2000-0  c.c. 

Less  —  Protecting   water,    10 ;    volume   of  electrode,   6; 

baryta  water  added  after  combustion,  20         v  »    .       36-°    » 

Gas  really  employed  for  the  test  .  .  .          "  .  .       1964-0  c.c. 

Reduced  to  15°  and  760  mm.  ...»       1741-0    „ 

20  c.c.  baryta  water  correspond  to  normal  oxalic  acid  .  .  20-6    „ 

Required  for  retitration  „  „  .  .'  4-3    „ 

Difference      .  „  „  v          16-3    „ 

Equal  to     .  .  .  .  .  .     0-93  per  cent.  CO2  by  vol. 

Deduct  CO2  previously  found  in  the  gas 

by  another  test       ....     0-33        „         CO2      „ 

Leaving  for  methane        ....     0-60        „        CH4      „ 

The  just-described  method  requires  an  electric  current 
which,  if  it  has  to  be  specially  produced,  makes  the  apparatus 
rather  complicated.  This  is  avoided  by  the  application  of 
the  Drehschmidt  platinum  capillary,  described  in  a  former 


276  TECHNICAL  GAS-ANALYSIS 

chapter  (p.  100),  in  connection  with  a  Hempel  pipette,  or  even 
with  an  Orsat  apparatus. 

Extremely  small  quantities  of  methane  (or  any  other 
combustible  gas)  can  be  burned  by  hot  cupric  oxide.  This 
method,  fully  worked  out  by  Fresenius,  has  been  employed  by 
Winkler  and  others  also  for  the  examination  of  pit-air.  The 
apparatus  and  method  are  fully  described  in  the  second  English 
edition  of  Winkler's  Technical  Gas-Analysis^  translated  by 
Lunge,  1902,  pp.  164  et  seq.  We  abstain  from  doing  so  here, 
as  the  somewhat  complicated  apparatus  and  manipulation 
required  make  that  method  hardly  count  as  a  "  technical "  one, 
and  it  will  be  but  rarely  applied  in  practical  cases.  We  have, 
moreover,  described  in  a  former  chapter  Jaeger's  process  for 
the  combustion  of  gases  by  means  of  cupric  oxide,  and  mentioned 
some  other  processes  of  this  class  (p.  172). 

Hempel  (Z.  angew.  Chem.,  1912,  p.  1841)  states  that  in  a 
Drehschmidt  platinum  capillary  (p.  100)  the  temperature  at 
which  methane  is  completely  burned  is  not  reached  when 
heating  by  a  Bunsen  burner,  but  complete  combustion  is 
obtained  by  employing  a  capillary,  made  of  well-fused  quartz, 
almost  entirely  filled  with  the  platinum  capillary.  Explosions 
are  prevented  by  passing  the  gaseous  mixture  very  slowly 
through  the  red-hot  capillary.  He  employs  quartz-glass 
tubes  also  for  the  Winkler  combustion  capillary  (p.  165). 
The  fractionated  combustion  of  mixtures  of  hydrogen  and 
methane  by  means  of  palladium  asbestos,  according  to  Cl. 
Winkler  (p.  165),  is  best  performed  by  means  of  a  Bunsen 
burner,  over  which  a  piece  of  brass  is  fixed,  on  which  the 
capillary  is  lying  in  a  mercury  bath.  The  heating  is  carried 
on  up  to  the  boiling  of  the  mercury  bath.  Opinions  differ 
as  to  the  accuracy  of  this  separation  of  hydrogen  and  methane 
by  fractionated  combustion,  but  Hempel  has  found  it  to  be 
perfectly  accurate,  if  care  is  taken  that  the  palladium  asbestos 
is  not  heated  beyond  400°,  which  is  easily  done  by  the  just- 
mentioned  apparatus,  and  if  the  gaseous  mixture  is  passed 
very  slowly  through  the  capillary.  He  also  worked  on  Paal 
and  Hartmann's  method  of  absorbing  the  hydrogen  by  colloidal 
palladium  (mixed  with  sodium  picrate),  avoiding  the  otherwise 
very  awkward  frothing  by  interposing  between  the  bulb  and 
the  capillary  of  the  absorbing-pipette  a  glass  tube,  2  c.c.  long, 


METHANE  277 

and  7  c.c.  wide,  containing  a  piece  of  platinum  wire-netting. 
He  describes  a  pipette  specially  adapted  to  this  purpose. 

Haber's  "  Schlagwetterpfeife "  (detonating-air  whistle). 
This  is  the  name  Professor  Haber  has  given  to  the  instrument 
invented  by  him  for  indicating  the  presence  of  a  dangerous 
percentage  of  methane,  etc.,  in  pit-air,  and  described  in 
Naturwissenschaften,  1913,  p.  1049,  Chem.  Zeit.,  1913,  p. 
1339,  and  /.  Soc.  Chem.  Ind.,  1914,  xxxiii.  p.  54.  He 
points  to  the  well-known  fact  that  the  Davy  pit-lamp 
does  not  with  certainty  prevent  explosions,  and  that  all 
the  other  indicators  for  this  purpose  have  drawbacks  in  one 
or  the  other  direction.  All  the  apparatus  based  on  chemical 
reactions  suffer  under  the  drawback  that  methane  reacts  only 
at  a  red  heat,  and  any  reactions  compelled  at  lower  tempera- 
tures are  not  reliable  for  pitmen's  purposes.  Therefore  Haber, 
with  the  co-operation  of  Dr  Leiser,  turned  to  physical 
indications.  They  first  improved  Rayleigh's  "Interferometer" 
to  such  an  extent  that  it  could  be  regularly  employed  under- 
ground by  experts,  and  allowed  to  judge  of  the  methane 
percentages  to  tenths  of  a  per  cent,  as  described  supra,  p.  177. 
It  is  founded  on  the  alterations  of  the  optical  density  of  the 
atmosphere  by  the  admixture  of  methane,  but  is  not  suitable 
for  use  by  pitmen  in  actual  work.  Therefore  Haber  and  Leiser 
turned  to  a  method  indicating  the  presence  of  methane  by 
acoustical  means,  already  indicated  by  Jahoda  in  the 
Transactions  of  the  Vienna  Academy  of  Sciences  in  the  year  1899, 
which  they  realised  by  the  construction  of  their  "  detonating- 
air  whistle,"  shown  in  Fig.  117. 

Within  a  smooth  cylinder,  a,  250  mm.  long  and  60  mm. 
diameter,  the  two  whistles,  for  air  and  for  the  gas,  are  placed. 
At  b  a  passage,  which  can  be  closed  by  a  small  screw,  leads  to 
the  air  whistle.  The  air  passes  downwards  in  the  direction  of 
the  arrow,  then  turns  upwards  up  to  the  small  mica  disc  <:,  then 
again  downwards,  rises  upwards  in  the  spiral  pipe  dy  and  issues 
at  e.  If  the  pipe  is  charged  in  this  way  with  pure  air  and  closed 
by  the  small  screw  at  by  the  air  is  retained  within  the  whistle 
by  the  action  of  the  narrow  spiral  </,  and  cannot  get  mixed  with 
the  pit-air,  whilst  the  spiral  pipe  allows  it  to  extend.  In  a 
similar  way  the  way  of  the  pit-gas  whistle  goes  first  downwards 
from  the  entrance /passes  a  filter  at  g,  and  a  layer  of  soda-lime 


278 


TECHNICAL  GAS-ANALYSIS 


at  //,  whereby  the  pit-air  is  purified  from  dust,  moisture,  and 
carbon  dioxide ;  it  then  goes  upwards  to  the  mica  disc  ty  then 
downwards,  and  ultimately  up  to  the  valve  /£,  through  which  it- 
passes  to  /,  where  a  tube,  not  indicated  in  the  diagram,  takes  it 
to  a  point  m,  from  which  it  passes  into  the  space  n.  The  latter 
forms  part  of  an  air-pump  which  is  set  into  motion  by  drawing 
the  cylinder  a  down.  If  thus  a  vacuum  is  produced  at  #,  the 

pit-gas  enters  at  f  and  proceeds  in 
the  above-stated  way.  If  now  the 
cylinder  a  is  let  go,  it  is  pulled  back 
by  the  vacuum,  produced  on  pulling 
down  over  the  plug  <?,  connected  with 
the  cylinder  ;  the  pit-gas  is  forced 
back  through  pipe  m,  past  the  closing 
valve  //  to  the  opening  valve  /,  and 
it  passes  through  r  and  q  to  the 
mouth-pieces  s  and  t  of  both  whistles, 
which  thereby  are  made  to  give  sound. 
The  air  and  the  pit-gas  in  the  whistle- 
tubes,  the  quality  of  which  determines 
the  height  of  the  sound,  are  tightly 
shut  off  from  the  gas  pressing  against 
them  by  the  thin  mica  discs  c  and 
i.  Thereby  it  has  been  ascertained 
that  the  contents  of  the  whistles, 
especially  that  of  the  pure  air  whistle, 
do  not  get  mixed  with  the  pit-gas 
blowing  against  them,  unless  they 
are  emptied  on  purpose.  In  order 
to  set  the  apparatus  into  motion, 
one  need  only  pull  down  the 


FIG.  1 1 7. 


cylinder  a  a  little  and  let  it  go  again.  The  sound  produced 
thereby,  which  beginning  from  I  per  cent,  methane  shows 
distinctly  countable  pulsations,  and  in  case  of  a  dangerous 
percentage  of  methane  a  rapid  tremulation,  is  audible  up  to  300 
ft.  in  a  straight  line.  A  drawback  of  this  instrument  is  that  it 
does  not  give  the  signal  automatically,  but  it  must  be  set  into 
motion  each  time,  whilst  the  flame  of  the  ordinary  pit-lamp  of 
its  own  accord  rises  up,  certainly  only  in  case  of  a  high  percent- 
age of  methane,  or  is  extinguished ;  small  percentages  of 


HYDROGEN  WITH  HYDROCARBONS  279 

methane  can  be  observed  only  by  screwing  down  the  flame,  and 
exact  observation. 


Mixtures  of  Hydrogen  with  Saturated  Gaseous  Hydro- 
carbons (Methane,  Ethane,  Propane,  etc.}. 

Lebeau  and  Damiens  (Comptes  rend.,  1913,  clvi.  pp.  144  and 
325)  cool  the  gaseous  mixture  either  by  liquid  air,  or  by  a 
mixture  of  solid  carbon  dioxide  and  acetone,  or  by  petroleum 
ether  cooled  by  liquid  air,  and  subject  it  then  to  fractional 
distillation.  Hydrogen  and  methane  cannot  be  separated  in 
this  way,  but  this  is  not  very  material,  since  such  a  mixture  can 
be  analysed  by  endiometric  combustion.  But  a  mixture  of 
hydrogen  and  ethane,  after  cooling  by  liquid  air,  can  be 
smoothly  separated  by  fractional  distillation  into  its  con- 
stituents. Mixtures  of  hydrogen,  methane,  and  ethane,  or  of 
hydrogen,  methane,  and  propane,  can  be  in  such  a  way  separated 
into  ethane  or  propane  on  the  one  side,  and  a  mixture  of 
hydrogen  and  methane  on  the  other.  The  composition  of  both 
these  mixtures  can  be  afterwards  ascertained  by  the  eudio- 
metric  method. 

In  order  to  analyse  eudiometrically  a  mixture  of  ethane, 
propane,  and  butane,  it  is  separated  into  two  fractions,  one  of 
which  contains  the  ethane  with  a  little  propane,  the  other  only 
isobutane  with  the  remainder  of  the  propane.  This  separa- 
tion is  effected  by  cooling  the  gaseous  mixture  below  —1  20°. 
The  presence  of  normal  butane  is  recognised  by  fractionating 
the  last  portions.  In  such  cases  where  the  gaseous  hydro- 
carbons are  mixed  with  the  vapours  of  liquid  hydrocarbons, 
first  of  all  by  cooling  down  to  -  78°,  all  the  gaseous  hydro- 
carbons, together  with  a  small  portion  of  the  vapours 
of  the  liquid  hydrocarbons  are  separated.  At  —  100°  the 
pentanes  do  not  possess  any  sensible  vapour  tension,  so  that 
the  gaseous  hydrocarbons  can  be  separated  from  them. 

This  work  is  continued  eodem  loco,  p.  557  (vide  Chem.  Zentralb., 
I9I3.  PP-  841,  1061,  1229;  and  Abstr.  Amer.  Chem.  Soc.,  1913* 
' 


Mathers  and  Lee  (Chem.  Eng.,  1913,  p.  159;  Chem.  News, 
1913,  cviii.  p.  80)  a  little  later  worked  out  an  entirely  similar 
method  for  the  determination  of  hydrogen,  methane  and 


280  TECHNICAL  GAS-ANALYSIS 

nitrogen.  They  point  out  that  combustion  of  these  gases  by 
explosion  with  oxygen,  the  method  generally  used  until  a  few 
years  ago,  in  consequence  of  the  incompleteness  of  the  combus- 
tions gives  too  high  a  result  for  nitrogen.  Much  better  is  the 
Winkler  method  (supra,  p.  92) ;  but  there  is  a  difficulty 
in  fastening  the  platinum  spiral  in  such  a  way  that  no  other 
metal  is  exposed  to  the  action  of  the  hot  oxygen,  and  if  the 
spiral  is  sealed  through  glass,  this  is  liable  to  crack.  A  source 
of  error,  always  present  when  effecting  the  combustion  over 
mercury,  is  the  oxidation  of  the  mercury  if  the  temperature  is 
too  high,  or  the  incompleteness  of  the  combustion  if  it  is  too  low. 
This  error  is  avoided  by  the  use  of  the  Drehschmidt  platinum 
capillary,  but  this  is  very  expensive.  Equally  good  results  are 
obtained  by  a  quartz  tube,  30-5  cm.  long,  7-25  mm.  outside  and 
3-38  mm.  inside  diameter,  filled  two-thirds  with  platinum  scrap, 
consisting  of  short  lengths  of  wire  (which  in  their  case  weighed 
I  I'lSp  g.).  A  mercury  pipette,  holding  the  gas  to  be  burned  and 
the  oxygen  required  for  the  combustion,  was  connected  to  one 
end  of  the  quartz  tube  by  a  capillary  tube  with  rubber  connec- 
tions. In  a  similar  manner  a  mercury  burette,  with  a  water-jacket, 
was  connected  to  the  other  end  of  the  quartz  tube,  pinchcocks 
being  placed  on  the  burette  and  on  the  pipette.  The  heating 
of  the  quartz  tube  was  effected  by  a  Bunsen  burner  with  a  wing 
tip,  producing  a  broad  flame,  an  asbestos  board  suspended  5 
mm.  above  the  tube  lessening  the  radiation  of  heat.  Before 
starting,  the  temperature  of  the  gas  [in  the  pipette  was  read ; 
the  pinchcock  connecting  the  burette  to  the  quartz  tube  was 
opened,  and  the  burner  lighted  for  three  minutes ;  the  increase 
of  the  volume  of  air  being  cared  for  in  the  burette.  Then 
the  pinch  cock  connecting  the  pipette  to  the  quartz  tube 
was  opened,  and  the  level  bottle  raised  so  that  the  gas  and 
oxygen  passed  slowly  over  the  hot  platinum,  generally  three 
minutes  being  required.  Then  the  gas,  by  means  of  the  level 
bottle,  was  forced  back  into  the  pipette,  and  again  into  the 
burette.  Now  the  flame  and  the  asbestos  board  were  removed, 
water  was  poured  over  the  quartz  tube  to  cool  it,  the  pinchcock 
on  the  side  of  the  burette  was  closed,  and  the  mercury  in  the 
burette  and  the  level-tube  levelled.  When  the  thermometer  in 
the  water-jacket  showed  constant  temperature,  the  volume  of 
gas  in  the  burette  was  read  and  corrected  for  variation  from  the 


ACETYLENE  281 

initial  temperature.  A  correction  must  be  made  for  the  CO2 
which  remains  in  the  quartz  tube  after  the  combustion. 

Marc  Landau  (Comptes  rend.,  1912,  civ.  p.  403  ;  Chem.  Zeit., 
1912,  p.  1385)  shows  how  by  the  application  of  ultra-violet 
rays  a  mixture  of  ethylene,  ethane,  and  hydrogen  can  be  analysed. 
First  the  unsaturated  hydrocarbon  is  polymerised,  the  ensuing 
contraction  of  volume  is  measured,  and  thereupon,  after  adding 
oxygen,  the  "  photo-combustion  "  of  the  saturated  hydrocarbons 
is  effected.  Daniel  Berthelot  and  Gaudechon  (Comptes  rend., 
civ.  p.  521  ;  Chem.  Zeit.,  1912,  p.  1472)  remark  that  pure 
methane  resists  to  the  ultra-violet  rays,  but  in  the  presence 
of  oxygen  hereby  a  far-reaching  condensation  takes  place, 
hydrogen,  carbon  dioxide,  and  water  being  consumed,  and 
paraffins,  not  attackable  by  sulphuric  and  nitric  acid,  being 
formed. 

Campbell  and  Parker  (Trans.  Chem.  Soc.,  1913,  p.  1292) 
burn  the  hydrogen  in  such  mixtures  by  palladium  black, 
heated  to  100°. 

Czako  (/.  Gasbeleucht.,  1914,  p.  169)  points  out  that  the 
previously  employed  absorbents,  especially  cuprous  chloride 
and  bromine  water,  always  take  up  as  much  methane,  hydrogen, 
and  nitrogen  as  corresponds  to  the  water  they  contain. 

ACETYLENE. 

We  have  already  mentioned  this  hydrocarbon  in  several 
places,  e.g.  pp.  118,  119,  132,  147. 

The  following  qualitative  reactions  have  been  described 
for  the  discovery  of  acetylene. 

Ilosvay  de  Nagy  Ilosvay  (Ber.,  1899,  p.  2698)  employs  the 
characteristic  formation  of  red  copper  acetylide  (Cu2C2H2)O 
in  the  following  way : — One  g.  cupric  sulphate  is  dissolved 
in  a  50  c.c.  flask  in  a  little  water,  4  c.c.  of  concentrated  liquor 
ammoniae,  and  then  3  g.  of  hydroxylamine  chloride  is  added ; 
the  solution  is  agitated  until  decolorised,  and  at  once  diluted 
up  to  the  mark.  A  few  cubic  centimetres  of  it  are  put  into 
a  500  c.c.  stoppered  cylinder,  the  gas  to  be  examined  for 
acetylene  is  passed  over  it,  until  the  colour  of  the  reagent 
changes  into  pink ;  the  cylinder  is  then  stoppered  and  agitated, 
whereupon  a  red  precipitate  is  formed,  if  acetylene  is  present. 
Or  else  the  gas  is  passed  through  a  small  bulb  tube,  containing 


282  TECHNICAL  GAS-ANALYSIS 

glass-wool  soaked  with  the  reagent.  This  reagent  keeps  about 
a  week  if  covered  with  petroleum,  but,  according  to  Pollak 
(quoted  by  Tread  well,  ii.  p.  533),  much  longer,  up  to  twelve 
months,  if  copper  wire  is  placed  in  it. 

Llorenz  (Chem.  Zeit.,  1912,  p.  702)  also  employs  the  reaction 
of  acetylene  on  cuprous  compounds.  Makowka  (ibid.,  p.  297) 
points  out  that  he  had  made  this  observation  long  before,  and 
published  it  in  detail  in  Z.  anal.  Chem.,  1907,  p.  125. 

Quantitative  Estimation  of  Acetylene. 

This  may  be  done  by  combustion  with  oxygen,  when  I 
vol.  C2H2  yields  2  vols.  of  CO2  ;  according  to  the  reaction  : 


2  vols.         5  vols.  4  vols. 

But  this  method  is  only  applicable  in  the  not  very  frequent 
cases  where  there  are  no  other  combustible  gases  present. 

Usually,  therefore,  acetylene  is  estimated  by  absorption 
in  ammoniacal  cuprous  chloride  solution,  or  in  fuming  sulphuric 
acid  (supra,  pp.  1  18  and  132),  or  by  means  of  its  silver  compounds, 
etc.  (p.  147). 

Lebeau  and  Damiens  (Bull.  Soc.  Chim.,  1913,  xiii.  p.  560) 
estimate  the  acetylenic  hydrocarbons  by  an  alkaline  solution 
of  potassium  iodomercurate,  and  the  ethylenic  hydrocarbons 
by  absorption  in  a  solution  of  uranyl  or  tungsten  or  molybdene 
sulphate  in  concentrated  sulphuric  acid. 

The  determination  of  the  yield  of  acetylene  from  calcium 
carbide,  which  does  not  belong  to  the  domain  of  technical 
gas-analysis  proper,  is  described  in  detail  in  the  paper  by 
Lunge  and  Berl,  in  Lunge's  Technical  Methods  of  Chemical 
Analysis,  translated  by  Keane,  vol.  ii.  pp.  590  et  sea.  (1911). 

Estimation  of  the  Impurities  contained  in  Crude  Acetylene. 

Crude  acetylene,  as  manufactured  from  commercial  calcium 
carbide,  may  contain  the  following  impurities  ;  up  to  4  per 
cent,  altogether  :  hydrogen  sulphide,  hydrogen  phosphide, 
ammonia,  carbon  monoxide,  hydrogen,  methane  (this  has 
never  been  proved  with  certainty),  nitrogen,  and  oxygen,  but 
only  the  two  first  of  these  are  seriously  objectionable,  as  they 


ACETYLENE  283 

impart  an  unpleasant  smell  to  the  gas,  render  it  poisonous, 
and  give  rise  to  injurious  acid  products  on  combustion. 
Ammonia  (which  occurs  only  in  traces)  is  also  objectionable, 
as  it  aids  in  the  formation  of  compounds  of  acetylene  with 
metals,  and  is  also  injurious  in  the  purification  by  bleaching- 
powder. 

The  estimation  of  hydrogen  sulphide  and  hydrogen  phosphide 
in  crude  acetylene  by  the  process  of  Lunge  and  Cedercreutz 
has  been  described  on  p.  150. 

Eitner  and  Keppeler  (/.  Gasbeleucht.,  1901,  p.  548)  state 
that  in  this  method,  where  the  acetylene  is  passed  through 
bleaching-powder  solution,  certain  organic  phosphides  are 
overlooked,  because  they  are  not  burned  to  phosphoric  acid 
by  the  hypochlorite  (according  to  Keppeler,  ibid.,  1904,  p.  62, 
in  this  operation  now  and  then  explosions  occur  through  the 
formation  of  nitrogen  chloride).  They  prefer  burning  the 
acetylene  by  means  of  oxygen  under  a  glass  hood,  as  described 
by  Drehschmidt  for  the  estimation  of  sulphur  in  coal-gas 
(p.  260),  and  passing  the  gases  through  two  ten-bulb  tubes, 
the  first  of  which  contains  water,  the  second  a  solution  of 
sodium  hypobromite  (prepared  from  caustic  soda  solution  and 
bromine),  then  through  an  empty  Peligot  receiver,  followed 
by  a  water-jet  pump,  by  which  the  current  of  gases  is  regulated 
in  such  manner  that  the  bubbles  in  the  ten-bulb  tubes  can  be 
just  counted.  Much  of  the  phosphorus  pentoxide  formed 
separates  already  in  the  glass  hood,  which  must  therefore  be 
washed  with  weak  hydrochloric  acid,  evaporating  the  washings 
with  addition  of  ammonium  bicarbonate,  in  order  to  separate 
any  silica  taken  out  from  the  glass ;  the  filtered  solution  is 
added  to  that  taken  out  of  the  bulb-tubes,  and  the  phosphoric 
acid  contained  therein  estimated  by  the  molybdene  method, 
the  sulphuric  acid  in  the  filtrate  therefrom  as  barium  sulphate. 
They  state  that  by  this  process  more  phosphorus  is  found 
than  by  the  hypochlorite  method.  According  to  Keppeler 
(ibid.,  1903,  p.  777)  the  combustion  may  be  carried  out  with 
atmospheric  air,  in  the  place  of  oxygen,  in  which  case  the 
gases  are  conducted  through  a  ten-bulb  tube,  the  first  bulbs 
of  which  contain  bits  of  "  Resistenzglas" ;  the  SO2  contained 
in  the  condensing  water  is  to  be  oxidised  by  bromine. 

According    to    Vogel    (Handbuch    fiir    Acetylen,    p.    273), 


284  TECHNICAL  GAS-ANALYSIS 

N.  Caro  had  worked  out  the  same  method  some  time  before, 
and  constructed  a  portable  apparatus  for  it.  By  the  com- 
bustion methods,  also  the  silicon  compounds  contained  in  the 
gas  can  be  estimated,  by  burning  the  acetylene  under  a  hood 
of  platinum  and  nickel,  passing  the  gases  through  pure  caustic 
soda  solution  (prepared  from  sodium),  adding  bromine  water, 
filtering  off  the  silicic  acid,  and  estimating  the  phosphoric  and 
sulphuric  acid  in  the  filtrate. 

Frankel  (/.  Gasbeleucht.,  1908,  p.  431)  combines  with  the 
above  method  an  estimation  of  the  yield  of  acetylene  from 
calcium  carbide. 

Lidholm  (Z.  angew.  Chem.,  1904,  p.  1452  ;  cf.  also  Hinrichsen, 
Chem.  Zentralb.)  1907,  ii.  p.  1356)  describes  another  apparatus 
for  this  purpose. 

Willgerodt  (Ber.t  1895,  P-  2107)  proposed  oxidising  the 
sulphuretted  and  phosphoretted  hydrogen  by  bromine  water; 
but  this  method  is  objectionable,  because  bromine  acts  too 
strongly  on  the  acetylene  itself. 

Mauricheau  (/.  Gasbeleucht.,  1908,  p.  257)  estimates  the 
phosphoretted  hydrogen  in  crude  acetylene  volumetrically. 
He  first  takes  out  H2S  and  NH3  by  caustic  potash  and 
sulphuric  acid,  shakes  up  the  remaining  gas  with  centinormal 
iodine  solution,  and  after  ten  minutes  retitrates  the  excess  of 
iodine.  Each  cubic  centimetre  of  centinormal  iodine  solution 
corresponds  to  0-055  c-c-  PH3  in  a  litre  of  acetylene  (at  15°  and 
760  mm.).  The  relation  between  the  iodine  solution  and  the 
phosphoretted  hydrogen  is  established  by  an  experiment  with 
crude  acetylene  of  known  contents  of  phosphorus. 

Hempel  and  Kahl  (Z.  angew.  Chem.,  1898,  p.  53)  measure 
the  crude  acetylene  in  a  gas-burette  filled  with  mercury,  force 
it  into  a  gas-pipe  filled  with  mercury  containing  3  c.c.  of  an 
acid  solution  of  cupric  sulphate  (prepared  from  1 5  g.  crystallised 
cupric  sulphate,  100  c.c.  water,  and  5  c.c.  of  dilute  sulphuric 
acid,  I  to  5  c.c.  water,  and  previously  saturated  with  acetylene), 
agitate  for  three  minutes,  and  measure  the  remaining  gas,  one- 
fourth  of  which  indicates  the  PH3.  (This  method  contains 
several  sources  of  inaccuracies.) 

Other  sulphur  compounds  (apart  from  H2S)  also  occur  in 
technical  acetylene,  as  shown  by  Lunge  and  Cedercreutz, 
loc.  cit.  This  is  mentioned  by  Moissan  and  others.  These 


ACETYLENE  285 

sulphur  compounds  are  oxidised  in  their  method  by  the 
hypochlorite  solution,  and  can  be  estimated,  if  solutions  free 
from  sulphuric  acid  are  employed  in  this  method. 

Ammonia  hardly  ever  occurs  in  sensible  quantities  in  crude 
acetylene,  and  never  in  such  quantities  that  it  can  be  estimated 
by  titration  ;  this  must  be  done  by  "  Nesslerising." 

According  to  the  rules  laid  down  by  the  German  Acetylene 
Union  (Chem.  Zeit.^  1906,  p.  607),  calcium  carbide  is  only  saleable 
if  the  gas  yielded  by  it  contains  at  most  0-04  per  cent, 
phosphorus  compounds,  calculated  as  hydrogen  phosphide. 
The  allowable  difference  of  analyses  is  o-oi  per  cent.  When 
fixing  the  hydrogen  contents  in  crude  acetylene,  all  the  gas 
must  be  driven  out  of  the  carbide.  If  the  small  quantities  of 
the  other  impurities  are  to  be  determined,  about  500  c.c.  of 
the  crude  acetylene  must  be  treated  with  Nordhausen  sulphuric 
acid  which  absorbs  acetylene  and  ammonia ;  the  other  gases 
must  be  determined  in  the  gaseous  remainder  by  the  ordinary 
methods  of  analysis. 

As  general  reagent  for  injurious  admixtures  in  crude 
acetylene,  Keppeler  (/.  Gasbeleucht.,  1904,  p.  461)  employs 
(as  Berge  and  Reychler  had  previously  done)  a  solution  of 
mercuric  chloride  containing  free  HC1,  in  which  those  impurities 
cause  a  precipitate.  It  is  convenient  to  employ  black  filtering 
paper,  soaked  with  mercuric  chloride  solution  (on  sale  by 
E.  Merck  in  Darmstadt),  which  before  the  test  is  moistened 
with  10  per  cent,  hydrochloric  acid,  and  held  over  an  open 
acetylene  burner,  without  lighting  the  gas.  In  the  presence 
of  phosphorus,  sulphur,  and  silicon  compounds,  a  white  spot 
appears  on  the  paper,  but  not  in  the  case  of  pure  acetylene. 

Gatehouse  (Acetylene,  1909,  p.  80)  recommends  white  paper 
soaked  in  an  ammoniacal  solution  of  silver  nitrate.  With 
properly  purified  acetylene  the  paper  will  remain  unchanged 
for  at  least  half  an  hour ;  with  impure  gas  it  will  become  black 
in  a  few  minutes. 

Rossel  and  Landriset  (Z.  angew.  Chem.,  1901,  p.  77)  analyse 
crude  acetylene  in  a  100  c.c.  Hempel  burette  filled  with 
mercury,  in  which  they  absorb  the  acetylene  by  30  c.c.  fuming 
sulphuric  acid ;  afterwards  they  estimate  oxygen  by  potassium, 
pyrogallate,  hydrogen  and  methane  by  the  explosion  pipette, 
and  the  oxygen  by  difference.  [Looking  at  the  small  volumes 


286  TECHNICAL  GAS-ANALYSIS 

in  question,  o-i  to  02  c.c.,  this  method,  where  the  gas  has  to  be 
carried  backwards  and  forwards  several  times,  is  most  un- 
certain.] 

A  complete  analysis  of  acetylene,  which  will  hardly  ever 
be  required  for  technical  purposes,  is  described  in  papers  by 
Haber  and  Oechelhauser,  von  Knorre  and  Arendt,  and  Frankel. 

ETHYLENE. 

As  we  have  noticed  in  several  places,  ethylene  can  be 
removed  and  estimated  by  absorption  by  fuming  sulphuric 
acid  (p.  118)  or  bromine  (p.  119),  but  this  becomes  more 
complicated  when,  as  is  mostly  the  case,  other  heavy 
hydrocarbons,  especially  benzene  vapour,  are  present. 

Berthelot  (Comptes  rend.)  Ixxxiii.  p.  1255)  proposed  first 
removing  the  ethylene  by  bromine  water,  and  subsequently 
benzene  by  fuming  nitric  acid ;  but  this  is  quite  incorrect, 
according  to  the  unanimous  judgment  of  Cl.  Winkler  (Z.  anal. 
Chem.,  xxviii.  p.  282),  Drehschmidt  (in  Post,  Chem.  -  techn. 
Analyse,  2nd  ed.,  i.  pp.  108  and  109),  and  Treadwell  and 
Stokes  (Ber.,  xxi.  p.  31). 

Drehschmidt  (Muspratt-Stohmann's  Techn.  Chemie,  4th  ed., 
iii.  p.  1 146)  draws  attention  to  the  fact  that,  as  already  de 
Wilde  had  shown  (Ber.,  vii.  p.  353),  in  the  absence  of  carbon 
monoxide  ethylene  and  its  homologues,  when  mixed  with 
hydrogen  and  passed  over  palladium  sponge  saturated  with 
hydrogen,  combine  with  hydrogen,  ethane  being  formed : 
C2H4+H2  =  C2H6.  He  believes,  however,  that  benzene  also 
combines  with  hydrogen,  and  he  proposes  calculating  the 
volumes  of  both  from  the  total  decrease  of  volume,  and  the 
specially  estimated  total  value  of  the  heavy  hydrocarbons. 

Independently  of  this,  Harbeck  and  Lunge  (Z.  anorg.  Chem. 
1898,  p.  27;  cf.  also  Lunge  and  Akunoff,  ibid.,  1900,  p.  191) 
equally  confirmed  the  addition  of  hydrogen  to  ethylene,  but,  in 
opposition  to  Drehschmidt,  they  showed  that  benzene  vapour 
does  not  combine  with  hydrogen,  which  would  admit  of 
separating  these  two  groups  of  hydrocarbons  (aliphatic  and 
aromatic)  from  each  other.  Unfortunately  they  had  equally 
to  establish  the  fact  that  this  involves  the  absence  of  carbon 
monoxide  —  a  circumstance  not  occurring  in  industrial  fuel 
gases. 


ETHYLENE  287 

It  seems  to  be  a  fact  that  the  action  of  bromine  and 
ethylene  differs  from  that  on  benzene  vapour,  inasmuch  as  the 
former  combines  with  bromine  to  form  the  stable  compound, 
C2H4Br2,  whilst  the  benzene  vapour  is  removed  as  a  mechanical 
mixture  with  bromine,  or  possibly  as  a  very  unstable  addition 
compound,  which  yields  up  the  bromine  to  any  substance 
readily  reacting  with  it,  such  as  potassium  iodide.  On  this 
difference  of  behaviour,  Haber  and  Oechelhauser  (/.  Gasbeleucht., 
1900,  xliii.  p.  347)  have  founded  the  following  method  for 
estimating  ethylene,  and  indirectly  benzene,  in  coal-gas. 

About  90  c.c.  of  the  gas  is  run  into  a  Bunte  burette,  the 
confining  water  sucked  out  in  the  usual  manner,  and  a  standard 
solution  of  bromine  water  (about  half  saturated)  allowed  to  run 
into  the  burette  up  to  a  definite  mark,  e.g.  the  5  c.c.  mark,  i.e., 
15  c.c.  of  bromine  water.  A  little  water  is  then  allowed  to 
enter  for  clearing  the  lower  capillary  tube  and  the  stopcock  of 
bromine  water,  and  the  burette  shaken  for  two  minutes,  after 
which  the  colour  of  bromine  vapour  should  still  be  distinctly 
visible.  After  further  three  minutes,  a  concentrated  solution  of 
potassium  iodide  is  sucked  into  the  burette,  and  several  times 
well  shaken  up.  Now  the  contents  of  the  burette  are  washed 
into  a  beaker,  where  the  liberated  iodine  is  titrated  by 
decinormal  thiosulphate  solution.  For  titrating  the  bromine 
water,  a  blank  test  is  made,  in  which  the  bromine  water  is 
sucked  up  into  the  burette  up  to  the  same  mark  as  in  the  other 
test.  The  difference  of  the  quantities  of  thiosulphate  consumed 
in  both  tests  shows  the  ethylene;  i  c.c.  \\n  thiosulphate  =1-2 
c.c.  ethylene  at  15°  and  760  mm. 

The  presence  of  homologues  of  ethylene  does  not  influence 
the  result,  because  the  number  of  affinities  combining  with 
bromine  is  the  same  for  equal  volumes.  But  according  to 
Fritzsche  (/".  Gasbeleucht.,  1902,  p.  281)  industrial  gases  contain, 
besides  the  hydrocarbons  of  the  ethylene  series,  other 
constituents  absorbing  bromine  (such  as  acetylene  and 
its  homologues),  so  that  the  just-described  method,  although 
sufficiently  accurate  for  coal-gas,  cannot  be  applied  to 
oil-gas. 

Tread  well  (Lehrbuch,  ii.  p.  534)  calls  Haber  and  Oechel- 
hauser's  method  recommendable  in  every  respect. 

In  the  presence  of  benzene  vapour,  this,  together  with  the 


288  TECHNICAL  GAS-ANALYSIS 

ethylene,  is  absorbed  by  fuming  sulphuric  acid  or  bromine 
water,  and  in  a  second  sample  the  ethylene  is  determined 
by  itself  as  just  described. 

In  the  presence  of  acetylene,  Tucker  and  Moody  (/.  Amer. 
Chem.  Soc.,  1901,  p.  671)  first  remove  this  by  an  ammoniacal 
silver  solution,  before  absorbing  the  ethylene  by  bromine 
water. 

Fritzsche  (loc.  cit.  and  Z.  angew.  Chem.,  1896,  p.  456)  estimates 
ethylene  by  treating  a  somewhat  large  volume  of  gas  with 
sulphuric  acid,  heating  in  a  water-bath,  subsequent  decom- 
position of  the  ethyl-sulphuric  acid  by  boiling  with  a  little 
water,  and  determining  the  alcohol  formed  by  an  estimation  of 
specific  gravity.  That  process  appears  too  troublesome  for 
technical  purposes.  According  to  this  author  butylene  and 
ethylene  can  be  separated  by  means  of  sulphuric  acid,  sp.  gr. 
1-620,  which  dissolves  only  butylene,  not  ethylene. 

An  indirect  qualitative  proof  for  the  presence  of  ethylene  in 
gas  mixtures  can  also  be  founded  on  the  fact  that,  like  some 
other  gases  and  vapours,  it  interferes  with  the  absorption  of 
oxygen  by  phosphorus.  The  percentage  of  ethylene  required 
for  this  purpose  is  stated  by  various  authors  from  0-05  up  to 
0-85.  (Details  in  Czako's  Beitrdge  zur  Keuntnis  natilrlicher 
Gasausstromungen,  1913,  p.  17.)  A  more  sensitive  reaction 
on  the  presence  of  ethylene  is  afforded  by  absorbing  it  in  a 
cold  saturated  solution  of  mercuric  acetate,  and  setting  it  free 
by  acidulating  the  reagent  (ibid.,  p.  19). 

BENZENE  (BENZOL). 

The  estimation  of  this  hydrocarbon,  together  with  other 
"  heavy  hydrocarbons,"  i.e.,  principally  the  members  of  the 
ethylene  series,  by  means  of  fuming  sulphuric  acid  or  bromine 
water,  has  been  mentioned  in  several  previous  places,  e.g.,  pp.  108 
and  119.  It  is,  however,  very  important  to  ascertain  the  per- 
centage of  benzene  vapour  by  itself,  as  it  is  the  principal  light- 
giving  constituent  of  coal-gas,  its  luminosity  on  burning  being 
about  six  times  that  of  ethylene. 

The  estimation  of  benzene  vapour  is  also  of  special 
importance  for  the  "cold  carburation"  of  coal-gas  and  water- 
gas,  as  proposed  by  Bunte  (J.  Gasbeleucht.,  1893,  p.  442),  and 


BENZENE  289 

in  the  gases  of  the  coking-process  by  distillation,  where  benzene 
is  obtained  as  a  commercial  product  even  from  poor  gases. 

We  now  proceed  to  the  description  of  the  methods  for 
estimating  benzene  vapour  in  gases,  not  yet  mentioned  in 
previous  chapters,  first  those  of  the  volumetric,  then  those  of 
the  gravimetric  and  other  classes. 

Volumetric  Methods. 

Hempel  and  Dennis  (/.  Gasbeleucht.,  1891,  p.  414)  recom- 
mended for  the  separate  absorption  and  estimation  of  benzene 
vapour  strong  alcohol  in, small  quantities.  But  later  on  Dennis 
himself,  together  with  O'Neill  (J.  Amer.  Chem.  Soc.,  1903,  p. 
503),  proved  the  unreliability  of  that  absorbent,  and  recom- 
mended instead  of  it  an  ammoniacal  solution  of  nickel  nitrate 
(16  g.  of  nickel  nitrate,  dissolved  in  180  c.c.  of  water  +  2  c.c. 
of  concentrated  nitric  acid,  poured  into  100  c.c.  liquor  ammonias 
0-908).  The  results  are  satisfactory,  as  confirmed  by  Stavorinus 
(Het  Gas,  1905,  p.  554).  Later  on  Dennis  and  McCarthy 
(J.  Amer.  Chem.  Soc.,  1908,  p.  233;  /.  Gasbeleucht.,  1908,  p.  1534) 
found  that  this  process  only  answers  in  the  presence  of  cyanogen 
compounds,  and  they  therefore  worked  out  a  process  founded 
on  the  application  of  an  ammoniacal  solution  of  nickel  cyanide, 
described  supra,  p.  108,  together  with  the  way  of  manipulating 
the  apparatus.  According  to  J.  Gasbeleucht.,  1912,  p.  891, 
this  method  yields  excellent  results. 

E.  Miiller  (J.  Gasbeleucht.,  1898,  p.  433)  absorbs  benzene, 
according  to  Bunte's  proposal  by  cooled  paraffin  oil  of  sp.  gr. 
0-88  to  0-89,  boiling  about  300°.  The  gas,  dried  by  calcium 
chloride,  is  passed  through  four  absorbing  vessels,  cooled  with 
ice  and  salt,  placed  in  series,  and  connected  in  such  manner 
that  glass  touches  glass  (which,  however,  as  found  by  Lunge, 
does  not  prevent  the  benzene  from  being  partly  absorbed  by 
the  india-rubber  joints).  The  current  must  be  slow,  say  2  c.c. 
per  second.  The  absorbed  portion  is  found  by  reweighing 
the  absorbers,  after  having  taken  the  temperature  of  the  room; 
the  volume  of  the  non-absorbed  portion  is  measured  in  a 
gas-meter.  This  process  is  employed  at  coke  works  for  the 
estimation  of  the  benzene  contained  in  the  gases,  which  on 
the  large  scale  is  recovered  by  a  precisely  similar  process. 

T 


290  TECHNICAL  GAS-ANALYSIS 

According  to  Pfeiffer  (Lunge  and  Berl's  Tech.  Chem.  Anal, 
iii.  p.  277)  it  is  not  accurate  enough  for  the  analysis  of 
illuminating  gas. 

As  previously  mentioned  (p.  109)  benzene  vapour  is 
completely  absorbed  by  bromine  water.  Since  it  is  a  fact  that 
benzene,  at  ordinary  temperature,  is  neither  brominated  nor 
oxidised  by  bromine,  it  was  difficult  to  understand  that  the 
absorption  of  benzene  by  bromine  should  be  really  complete 
and  quantitative.  This  was  again  established  by  Treadwell 
and  Stokes  (Ber.t  1888,  p.  3131),  and  confirmed  by  Haber  and 
Oechelhauser  (J.  Gasbeleucht.,  1896,  p.  ,804,  and  xxix.  p.  2700). 
Haber  supposed  this  absorption  to  be  merely  a  physical  process, 
and  this  has  been  confirmed  by  Korbuly  (Inaugural  Dissertation, 
Zurich,  1902).  Just  as  bromine  can  be  removed  from  an 
aqueous  solution  by  shaking  with  benzene,  so,  vice  versa, 
benzene  can  be  removed  by  shaking  with  bromine,  or  even 
with  ethylene  bromide,  etc. 

Nitric  acid  of  the  highest  degree  of  concentration  (sp.  gr. 
1-52)  also  absorbs  the  benzene,  but  this  process  cannot  be 
employed  in  the  presence  of  carbon  monoxide,  as  this  gas  is 
thereby  completely  oxidised  to  carbon  dioxide,  which  on 
removing  the  acid  vapour  by  caustic  potash  solution  is  removed 
together  with  the  benzene. 

Estimation  of  Benzene  in  the  Form  of  Dinitrobenzene. — A 
mixture  of  fuming  nitric  acid  and  concentrated  sulphuric  acid 
converts  the  small  quantities  of  benzene  vapour  occurring  in 
gaseous  mixtures  quantitatively  into  dinitrobenzene,  which 
can  be  easily  traced,  as  it  is  little  soluble  in  water,  but  easily 
soluble  in  ether,  whilst  the  products  of  the  reaction  of  that 
acid  mixture  on  ethylene  are  easily  soluble  in  water,  and  are 
not  extracted  by  ether.  On  this  behaviour  Harbeck  and 
Lunge  (Z.  anorg.  Chem.,  1898,  p.  41)  found  a  method  for  the 
estimation  of  benzene  in  the  presence  of  ethylene. 

The  fifteen-bulb  tube  K,  Fig.  118,  is  charged  with  about 
no  c.c.  of  a  mixture  of  equal  volumes  of  concentrated  pure 
sulphuric  acid  and  pure  fuming  nitric  acid,  sp.  gr.  1-52.  After 
this  tube  follow  the  two  washing-bottles  h  and  tt  charged  with 
caustic  soda  solution  for  retaining  acid  vapours;  then  the 
gas-measuring  bottle  M,  filled  with  water,  closed  by  a  cork 
with  four  perforations,  put  on  air-tight  by  means  of  sealing 


BENZENE 


291 


wax,  through  which  passes  the  gas-conduit  gy  the  syphon-tube 
n  for  running  out  the  water,  the  mercurial  pressure  gauge  my 
and  the  thermometer  t.  Tube  n  ends  about  20  cm.  below  the 
bottom  of  the  bottle  in  a  fine  point ;  tap  q  serves  for  regulating 
the  outflow  into  the  measuring-flask  v.  Wherever  it  is 
unavoidable  to  employ  rubber  joints  in  the  parts  through 
which  the  gas  current  flows,  they  must  be  secured  by  wire 
fastenings  and  painted  with  a  solution  of  shellac.  Wherever 
the  rubber  comes  into  contact  with  nitric  acid  vapours,  it  must 
be  protected  on  the  inside  by  greasing  with  vaseline. 


FIG. 118. 

The  manipulation  is  as  follows: — Before  the  experiment 
the  air,  enclosed  in  M  above  the  water,  is  under  atmospheric 
pressure  ;  the  column  of  mercury  in  both  limbs  of  the  gauge- 
tube  m  must  stand  at  the  same  level.  Now  the  tube  /  at  the 
other  end  is  connected  with  the  gas-conduit,  and  the  screw 
clamp  q  is  opened  so  far,  that  the  water  in  M  flows  in  a  thin 
jet  into  flask  v,  with  a  velocity  of  about  6  litres  per  hour.  The 
pressure  in  M  must  suffer  as  little  change  as  possible.  The 
running-off  water  must  be  measured.  Towards  the  end  of 
the  test,  when  about  200  c.c.  less  than  10  litres  has  run  out, 
pinchcock  q  is  opened  further,  so  that  flask  c  is  quickly  filled 
and  a  little  minus-pressure  is  produced  in  M.  Now  q  is  closed, 
but  the  introduction  of  gas  is  continued,  until  the  pressure 


292  TECHNICAL  GAS-ANALYSIS 

gauge  m  again  indicates  atmospheric  pressure.  For  this 
purpose  the  inlet-ends  of  the  tubes  in  bottles  h  and  i  must  be 
drawn  out  of  the  liquid,  and  the  bulb-tube  K  must  be  put  in 
a  horizontal  position.  If  during  the  experiment,  which  goes 
on  for  about  two  hours,  the  temperature  and  barometric 
pressure  have  not  changed,  10  litres  of  gas  have  been  sent 
through  the  apparatus,  plus  the  volume  of  the  heavy  hydro- 
carbons retained  by  the  nitrating  mixture  and  the  carbon 
dioxide  contained  in  the  gas,  which  has  been  absorbed  in  the 
washing-bottles,  both  of  which  constituents  must  be  estimated 
in  another  sample  of  the  gas.  The  temperature  of  the  gas 
and  the  barometric  pressure  must  be  noted. 

In  order  to  separate  the  dinitrobenzene  retained  in  the 
acid  mixture,  the  contents  of  bulb-tube  K  are  emptied  out  into 
a  beaker  holding  2  litres,  and  one-third  filled  with  a  mixture  of 
ice  and  water,  and  K  is  rinsed  out  with  water.  The  acid  solu- 
tion is  neutralised  with  about  300  c.c.  caustic  soda  solution 
(i  :  3),  cooling  with  ice.  On  prolonged  standing,  most  of  the 
dinitrobenzene  separates  out  as  a  mass  of  fine,  almost  white 
crystals,  partly  floating  on  the  surface  of  the  liquid.  The  clear 
liquid  is  poured  through  a  filter,  spread  on  a  small  aspirating 
contrivance,  upon  which  also  the  crystals  are  brought  and 
washed,  until  the  water  running  through  gives  no  more  reaction 
on  sulphuric  acid.  The  crystals  are  dried  at  70°  to  80°,  or  over 
sulphuric  acid,  and  weighed.  In  order  to  recover  also  the 
dinitrobenzene  dissolved  in  the  filtrate  and  washings,  the  whole 
liquid  is  diluted  to  a  round  volume,  say  2250  c.c. ;  one-tenth  of 
it,  in  this  instance  225  c.c.,  is  put  into  a  glass-tap  bulb,  where  it 
is  twice  shaken  up  with  50  c.c.  ether,  ten  to  fifteen  minutes  each 
time.  From  the  united  liquids  the  ether  is  distilled  off  in  a 
round-bottomed  flask,  the  last  portions  of  ether  and  water  being 
removed  by  a  current  of  air.  The  residue  still  contains  salts, 
insoluble  in  absolute  ether.  It  is  taken  up  with  such  ether, 
filtered  into  a  tared  glass  dish  and  washed.  After  evaporating 
the  ether,  the  previously  dissolved  quantity  of  dinitrobenzene 
is  found,  multiplied  by  ten,  and  added  to  the  principal  quantity 
previously  found.  From  the  total  quantity  of  dinitrobenzene, 
the  benzene  is  calculated  by  multiplying  it  with  0-4603. 

In  order  to  reduce  the  weight  to  volume,  we  take  notice  that 
I  litre  benzene  vapour  at  o°  and  760  mm.  pressure  weighs 


BENZENE  293 

3-5821,  measured  dry,  and  that  the  density  of  aqueous  vapour  is 
equal  to  one-fortieth  of  that  of  benzene  vapour.  If  we  denote  the 
temperature  of  the  gas  =  /,  the  state  of  the  barometer  =  b,  the 
tension  of  aqueous  vapour  =  e,  the  contents  of  the  gas  in  volume- 
per  cent.  CO2  and  CnHm  =  s\  the  weight  of  dinitrobenzene  =  N 
grammes,  the  volume  of  the  gaseous  remainder  in  bottle  W  =  W, 
the  percentage  of  benzene  vapour  in  the  gas  is  : 

C.H.  =  98.505  N(i  +  0.3665*)  (IPO  -*)  per  cent  by  volume. 


40 

PfeifTer  (/.  Gasbeleucht.,  1899,  p.  697;  Chem.  Zeit.,  1904,  p.  884) 
points  out  that  in  the  presence  of  carbon  monoxide  this  is  also 
partly  oxidised  by  the  nitrating  mixture.  He  carries  out  the 
dinitrobenzene  method,  not  with  a  current  of  gas,  but  with  a 
certain  volume  of  gas  at  rest.  This  allows  of  dispensing  with 
the  cooling  by  ice,  but  the  product  of  the  reaction  must  be 
purified  by  means  of  blood-charcoal.  The  dinitrobenzene  is 
not  weighed,  on  account  of  the  losses  in  drying,  but  titrated 
with  stannous  chloride  by  the  method  of  Limpricht  (Ber.>  1878, 

P-  35): 

-  R. 


The  only  apparatus  for  measuring,  nitrating,  and  extraction 
with  ether  is  a  glass  tap  bulb-tube,  with  glass  stopper,  holding 
\  litre,  the  contents  of  which  are  exactly  measured.  Before 
the  experiment,  the  glass  tap  and  the  stopper  are  moistened 
with  a  drop  of  sulphuric  acid.  The  bulb-tube,  after  taking  out 
the  stopper,  is  put  in  a  stand,  bottom  upwards,  and  is  filled 
from  above  with  the  gas  to  be  tested,  which  after  two  minutes 
has  driven  out  the  air.  The  tap  is  closed,  the  conducting  tube  is 
removed,  the  tap  is  opened  for  a  moment  in  order  to  make  the 
pressure  equal  to  that  of  the  atmosphere,  noting  both  this  and 
the  temperature  of  the  room.  Now  2  c.c.  of  the  acid  mixture 
(made  of  equal  parts  of  concentrated  sulphuric  acid  and  strongly 
fuming  nitric  acid)  is  poured  into  the  running-ofF  tube,  which 
still  points  upwards.  By  opening  the  tap,  the  acid  is  cautiously 
run  into  the  bulb  up  to  the  last  drop,  and  is  made  to  wet  the 
inner  surface  all  over  by  repeatedly  inclining  the  bulb.  After 
half  an  hour  the  absorption  of  the  benzene  is  complete.  The 
liquid  is  again  made  to  moisten  all  the  inner  walls  of  the  bulb, 


294  TECHNICAL  GAS- AN  A  LYSIS 

30  c.c.  of  a  concentrated  solution  of  sodium  carbonate  is  rapidly 
poured  in  through  the  mouth  of  the  bulb,  and  this  is  shaken 
until  there  are  no  more  vapours  visible.  In  case  of  necessity 
the  neutralisation  is  finished  by  adding  more  sodium  carbonate, 
and  at  last  the  liquid  is  slightly  aciduated  by  hydrochloric  acid. 
No  special  indicator  is  needed ;  the  reaction  is  sufficiently 
indicated  by  the  change  of  the  colour  from  orange-red  (alkaline) 
to  wine-yellow  (acid).  By  shaking,  first  of  all  the  excess  of 
carbon  dioxide  is  removed.  Then  the  nitrated  product  is 
extracted  by  twice  shaking  up  with  50  c.c.  of  ether  during  five 
minutes,  and  placed  in  a  small  flask  containing  i  g.  sharply 
dried  carbonate  of  potash  and  0-5  g.  fine  blood-charcoal.  The 
mixture  which  at  first  shows  a  strong  yellowish  red  colour,  is 
allowed  to  stand  for  several  hours,  repeatedly  shaking  it. 
It  is  then  filtered  into  a  200  c.c.  measuring-flask,  rinsed  into  it 
with  absolute  ether,  and  placed  on  a  water-bath  for  driving  off 
the  solvent.  When  this  has  been  achieved,  about  10  c.c. 
alcohol  and  exactly  10  c.c.  of  a  stannous  chloride  solution  (150  g. 
tin,  dissolved  in  hydrochloric  acid,  50  c.c.  concentrated  hydro- 
chloric acid,  diluted  with  water  to  i  litre)  is  added, and  the  mixture 
heated  for  ten  minutes  on  a  water-bath.  Now  water  is  put  into 
the  flask  up  to  the  mark,  and  20  c.c.  of  the  mixture  (equal  to  one- 
tenth)  is  titrated  with  decinormal  iodine  and  starch  (  =  a).  The 
stannous-chloride  solution  is  standardised  by  another  experi- 
ment, heating  10  c.c.  of  it  with  10  c.c.  alcohol  in  a  200  c.c.  flask 
for  ten  minutes,  diluting  up  to  the  mark,  and  titrating  with 
iodine  solution  (  =  £).  The  difference  b  —  a  shows  the  consump- 
tion of  iodine  for  the  dinitrobenzene,  whose  weight  is  : 

=  (b  —  d)io  x  0-0014  g« 

The  calculation  of  the  weight  of  dinitrobenzene  for  volume- 
per  cent,  of  benzene  vapour  in  the  illuminating  gas  examined 
is  based  on  the  following  data : — i  g.  dinitrobenzene  =  0-4643 
g.  benzene ;  I  g.  benzene  =  279-2  c.c.  vapour  at  o°  and  760  mm. 
pressure.  If  we  denote  the  weight  of  the  dinitrobenzene 
ascertained  as  above,  g,  and  the  volume  of  gas  employed  (i.e., 
the  contents  of  the  bulb-funnel  J),  the  percentage  in  volume  of 
benzene  vapour  in  the  gas  is  : 


v*/-,  .  ^760     100        36000  273 +  / 

gx  0-4643  x  279-2  v   '*    £      x  -j-  =  1-f-  x  g  x   -M-, 


BENZENE 


295 


(In  the  place  of  the  quotient  36090 :  J,  of  course,  a  constant 
magnitude  for  the  bulb-funnel  employed  may  be  introduced.) 

According  to  the  analyses  quoted  by  Pfeiffer,  this  method 
yields  results  sufficiently  in  accordance  with  those  obtained  by 
the  Harbeck-Lunge  method,  and  the  nickel  nitrate  method  of 
Dennis  and  O'Neill  (supra,  p.  289). 


Estimation  of  Benzene  Vapour  by  Freezing. 

H.  Ste.  Claire  Deville  (/.  Gasbeleucht.,  1889,  p.  652)  proposed 
separating  the  benzene  from  gaseous  mixtures  by  cooling 
down  to  a  constant  temperature  of —22°  C,  and  weighing  the 
crystallised  benzene.  The  weight  thus  found  must  be  increased 


FIG.  119. 


FIG.  120. 


by  23-5  g.  benzene  per  I  cb.m.  gas,  which  quantity  remains  in 
the  gas,  cooled  down  to  —22°.  The  condensed  benzene  is 
taken  up  in  the  glass  serpentine  coil,  shown  in  Fig.  119,  about 
7  mm.  wide  inside,  closed  by  rubber  stoppers  and  weighed 
before  the  experiment.  It  is  then  placed  in  a  freezing-mixture, 
as  shown  in  Fig.  120,  contained  in  a  thick-walled  vessel,  pro- 
vided with  an  outlet  at  the  bottom  for  water  dropping  out. 
The  freezing-mixture  consists  of  3  litres  crushed  ice  and  0-6 
litre  cattle-salt.  A  thermometer  placed  in  the  same  vesse 
ought  to  show  a  pretty  constant  temperature  of  —22°. 

Before  introducing  the  gas  into  the  serpentine  coil,  it  must 


296  TECHNICAL  GAS-ANALYSIS 

be  well  dried  in  a  calcium-chloride  tower.  The  connection 
with  the  coil  is  made  by  a  very  short  rubber  tube.  Behind 
the  apparatus  is  placed  a  gas-meter  for  measuring  the  gas 
passed  through,  with  a  thermometer  ;  the  temperature  should 
be  again  that  of  the  room.  The  benzene  separates  in  the  coil 
in  a  solid  form.  If  this  should  cause  the  coil  to  be  stopped  up, 
it  must  be  carefully  taken  out  of  the  freezing-mixture  and  for 
a  moment  placed  in  water,  so  that  the  benzene  fuses  and 
collects  in  the  bulb  below  the  coil ;  after  this  the  passage  of 
the  gas  through  the  cooled  coil  can  go  again.  The  experiment 
should  be  kept  going  on  for  six  or  eight  hours,  at  the  rate  of 
150  litres  gas  per  hour.  Then  the  coil,  again  closed  by  the 
rubber  stoppers,  is  weighed,  the  increase  of  weight  indicating 
the  quantity  of  benzene  separated  from  the  gas.  This  quantity 
is  calculated  upon  i  cb.m.  gas,  and  increased  by  the  constant 
figure  23-5  g.  One  g.  benzene  =  279-2  c.c.  benzene  vapour 
at  normal  conditions.  If  the  weight  of  the  condensed  benzol 
is  put  =  gt  the  volume  of  gas  employed  (in  litres)  =  Vx,  /  its 
temperature  and  b  the  pressure,  the  volume-percentage  of 
benzene  in  the  gas  is : 


According  to  Deville's  experiments,  it  is  not  necessary  to 
employ  a  second  coil  for  the  complete  separation  of  the  benzene. 
An  advantage  of  the  process  is  the  possibility  of  examining  the 
quality  of  the  condensed  product  by  distillation,  but  the  method 
is  too  troublesome  for  checking  the  daily  work. 

Calculation  of  the  Amount  of  Benzene  Vapour  from  the 
Specific  Gravity. 

Pfeiffer  (Lunge  and  Berl's  Untersuchungsmethoden^  iii.  p. 
275)  makes  an  approximate  estimation  of  the  benzene  vapour 
in  coal-gas  from  its  specific  gravity,  and  the  total  quantity  of 
heavy  hydrocarbons,  CnHm>  present  in  the  gas.  First,  from 
the  total  analysis  and  the  experimentally  determined  specific 
gravity  of  the  gas,  the  specific  gravity  of  the  heavy  hydro- 
carbons, CnHm)  is  calculated  by  the  rules  given  in  a  previous 


BENZENE 


297 


chapter   (p.    179).     We   further   take  notice  that   according  to 
series  a  the  specific  gravities  /3  are  as  follows : — 


a. 

I 

a.  Ethylene  (C2H4)       . 
Propylene  (C3H6)     . 

0-9674 
1-4550 

\  CnB^n 

10689 

b.  Benzene  (C6H6) 
Toluene  (C7H8) 

2-7041 
3-I875 

}CnIl2n-6 

2-8008 

Experience  has  shown  that  in  coal-gas  the  higher 
homologues  of  the  groups  a  and  b  are  only  present  in 
very  small  proportions ;  we  assume  here  that  they  amount 
to  about  one-fifth  of  the  fundamental  substance,  which  leads 
to  calculating  the  average  specific  gravities  of  the  two  groups 
CnH2n  and  CnH27l_6,  as  stated  sub  /3.  Mixtures  of  the  two 
groups  will  hence  possess  an  average  specific  gravity,  which 
is  always  between  the  two  limits  i-o  and  2-8;  it  will  be  nearer 
one  or  the  other  of  these  values,  the  more  the  gases  or 
vapours  of  the  corresponding  groups  are  present.  Quite 
generally  the  volumes  of  the  two  groups  will  be  in  inverse 
proportion  to  one  another,  as  the  differences  of  their  specific 
gravities  against  the  calculated  specific  gravity  s  of  the  mixture 
f  IT 

CMH2n :  C,,H2w_6  =  (2-8  -*):(*-  i-o). 

Hence  the  contents  of  benzene  vapour  in  each  (2-8 -j) 
H-(J  —  i-o)  volumes  of  heavy  hydrocarbons  is  =  (.$•—  i-o)  volumes, 
and  in  the  total  quantity  of  heavy  hydrocarbons 


(CMHm) 


(f- 1.0)0,11,.  (j-i.o)C,Ht 

(2.S-s)  +  (s-i.o)  1.8 

per  cent,  benzene  by  volume. 


Let  us  suppose,  for  instance,  that  we  have  3-7  per  cent, 
heavy  hydrocarbons  (CnHTO),  and  their  specific  gravity  s 
calculated  =1-7939;  fr°m  this  follows,  according  to  the  formula 
just  given,  benzene  vapour  =  1-6  per  cent,  and  ethylene  =  2-1 
per  cent. 

The  experiments  made  by  Pfeiffer  showed  that,  in  spite 
of  some  objections  which  might  be  made  against  the  above- 
described  estimation  of  benzene  by  calculation,  in  the  case  of 


298  TECHNICAL  GAS-ANALYSIS 

illuminating  gas  the  results  agree  very  well  with  those  of  the 
best  methods  for  estimating  the  benzene.  But  of  course  that 
way  will  be  only  taken,  if  the  data  for  the  calculation  need 
not  be  specially  ascertained  for  this  purpose,  but  can  be 
occasionally  used. 

An  apparatus  for  the  estimation  of  benzene  in  coal-gas 
founded  on  passing  the  gas  through  a  known  quantity  of 
benzene  up  to  saturation,  is  described  in  the  Ger.  P.  267491 
of  the  Societe  Roubaisienne  d'Eclairage  par  le  Gaz,  and 
R.  R.  L.  H.  Forrieres. 

General  Remarks  concerning  the  Estimation  of  Benzene 
Vapour  in  Gases. 

Benzene  vapour  is  very  sensibly  absorbed  by  water  and  by 
all  aqueous  solutions  of  salts.  Treadwell  (Lehrbuch^  ii.  p.  532) 
quotes  special  experiments  made  in  that  respect  by  Korbuly, 
with  water  and  caustic  potash  solution.  When  analysing  gases 
containing  carbon  dioxide  and  benzene,  always  first  the  CO2 
is  absorbed  by  caustic  potash,  and  subsequently  the  benzene 
by  fuming  sulphuric  acid  or  bromine  water.  But  both  esti- 
mations will  be  wrong,  if  fresh  caustic  potash  solution  is 
employed  for  absorbing  the  CO2,  for  it  will  not  merely  absorb 
the  whole  of  the  CO2,  but  also  very  much,  possibly  nearly  all 
the  C6H6.  The  results  are  only  to  be  trusted  if  the  caustic 
solution  is  previously  saturated  with  benzene,  which  will  be 
the  case  after  prolonged  use. 

This  objection,  of  course,  does  not  apply  to  the  special 
methods  for  the  estimation  of  benzene,  described  in  the  present 
chapter,  which  are  applied  to  large  quantities  of  gas,  not 
previously  treated  with  caustic  liquor  or  other  aqueous 
solutions. 

NAPHTHALENE  VAPOUR. 

Although  most  of  the  large  quantities  of  naphthalene  pro- 
duced from  the  coal  during  its  distillation  is  condensed  in  the  tar, 
yet  the  small  quantity  of  naphthalene  vapour  left  in  the  purified 
gas  (which  rarely  exceeds  15  or  20  grains  per  cubic  foot) 
frequently  causes  great  trouble  by  depositing  in  the  solid 
state  in  the  gas  mains.  This  had  led  to  applying  special 
methods  for  removing  the  naphthalene  from  the  crude  gas 


NAPHTHALENE  299 

by  washing  or  cooling,  and  its  estimation  in  the  gas  is  therefore 
useful  for  testing  the  working  of  such  apparatus. 

No  satisfactory  method  is  as  yet  known  for  estimating  the 
amount  of  naphthalene  present  in  the  gas  still  containing  tar 
owing  to  the  difficulty  of  separating  the  tar-fog,  without  at  the 
same  time  removing  part  of  the  naphthalene  present  as  vapour ; 
but  for  the  cooled  gas  free  from  tar-fog,  several  methods  are 
used,  all  of  which  depend  on  the  fact  that  naphthalene  combines 
with  picric  acid  to  form  the  crystalline  picrate,  C10H8 .  C6H3N3O7, 
fusing  at  147°,  which  is  practically  insoluble  in  picric  acid 
solution,  although  it  is  partly  dissociated  into  its  constituents 
by  water.  This  way  of  estimating  the  naphthalene  has  been, 
e.g.,  employed  by  Kiister  (Ber.,  1894,  p.  1101). 

Colman  and  Smith  (/.  Soc.  Chem.  Ind.,  1900,  p.  128)  pass 
the  gas  through  a  series  of  three  absorbing  bottles,  charged 
with  a  nearly  saturated  solution  of  picric  acid  in  water,  about 
one-twentieth  normal,  of  which  100  c.c.  is  used  in  the  first,  and 
50  c.c.  in  each  of  the  other  two  bottles.  The  gas  is  first  passed 
through  a  bottle  charged  with  citric  acid  solution,  to  remove 
ammonia,  which  would  otherwise  neutralise  some  of  the  picric 
acid,  and  then  bubbled  through  the  latter  at  the  rate  of  \  to 
i  cb.  ft.  per  hour,  until  10  to  15  cb.  ft.  have  passed  through. 
The  whole  of  the  naphthalene  is  thus  taken  out  of  the  gas 
(already  the  first  bottle  removes  all  but  traces)  and  separates 
as  naphthalene  picrate,  which,  however,  undergoes  a  partial 
dissociation  linto  free  naphthalene  and  picric  acid.  To  effect 
the  complete  conversion  of  the  naphthalene  into  picrate,  the 
method  of  Kiister  (loc.  cit.)  is  followed.  According  to  this  the 
contents  of  the  absorption  bottles  are  washed  with  as  small 
a  quantity  of  water  as  possible  into  a  narrow-mouthed  bottle 
of  such  size  that  it  is  nearly  filled  with  the  liquid  ;  this  bottle  is 
then  closed  by  a  rubber  cork,  through  which  passes  a  glass 
tube,  closed  at  the  lower  end,  but  having  a  small  hole  blown 
in  the  side  about  I  in.  from  the  bottom.  The  tube  is  placed 
so  that  this  hole  is  just  below  the  bottom  of  the  stopper,  and 
the  bottle  then  evacuated  as  completely  as  possible  with  a 
water-jet  pump ;  whilst  the  pump  is  still  working,  the  tube  is 
raised  so  that  the  small  hole  is  well  above  the  bottom  of  the 
stopper,  the  bottle  being  thus  sealed.  It  is  then  placed  in  a 
water-bath  containing  sufficient  water  to  cover  it,  the  water 


300  TECHNICAL  GAS-ANALYSIS 

heated  to  the  boiling-point,  and  the  heating  continued  until 
the  liquid  is  quite  clear.  The  bottle  is  then  allowed  to  cool, 
with  occasional  shaking  to  wash  down  any  naphthalene  sublimed 
into  its  upper  portion.  After  standing  overnight,  the  naphtha- 
lene picrate  is  separated  completely  and  is  filtered  off  on  the 
pump,  and  the  precipitate  washed  with  a  small  quantity  of  water. 
When  too  much  water  is  used,  the  results  are  too  low.  It  is 
therefore  preferable  to  pour  the  contents  of  the  bottle  into 
a  measuring  cylinder,  and  note  the  volume  ;  then  to  filter 
through  a  dry  filter-paper,  rejecting  the  first  few  cubic  centi- 
metres of  filtrate,  and  to  titrate  100  c.c.  of  the  filtrate  with  n/io 
potassium  hydroxide.  The  indicator  may  be  phenolphthalein 
or  lacmoid,  or  methyl  orange.  If  n  =  volume  in  cubic  centi- 
metres of  the  liquid  after  heating,  and  v  the  number  of  cubic 
centimetres  of  decinormal  alkali  required  for  100  c.c.  of  the 
filtrate,  the  volume  of  decinormal  alkali  required  for  the  whole 

solution  is  —  '-    -  =  V.      The  alkali  equivalent  of    100   c.c.  of 
100 

picric  acid  solution  originally  used,  called  V1,  is  ascertained 
by  titration  with  decinormal  alkali  in  a  similar  manner,  and 
the  difference  between  V1  —  V  shows  the  quantity  of  decinormal 
alkali  corresponding  to  the  picric  acid  removed  by  combination 
with  naphthalene.  One  c.c.  of  decinormal  alkali  corresponds  to 
0-0229  g-  °f  picric  acid,  and  therefore  to  0-0128  g.  or  0-1975 
grain  of  naphthalene,  as  229  parts  of  picric  acid  combine  with 
128  parts  of  naphthalene.  The  number  of  grains  of  naphtha- 
lene per  100  cb.  ft.  is  : 


(V1  -  V)  X  IOO  X  O.IQ7q  .         ^     TT 

\=r-.  -  '-  —  7  —  y'D  =  grams  C10HS  per  100  cb.  ft. 

Volume  of  gas  present 

PfeifTer  (Lunge  and  BerPs  Untersuchungsniethoden,  iii.  p.  304) 
proceeds  as  follows  :  —  He  employs  a  Pettenkofer  tube,  30  cm.  long 
and  2  cm.  wide,  charged  with  1  5  c.c.  of  picric  acid  solution,  prepared 
by  dissolving  15  g.  picric  acid  in  2  litres  water,  and  filtering 
after  complete  cooling.  In  order  to  avoid  the  evaporation  of 
water  from  this  liquid,  and  at  the  same  time  to  retain  the  last 
traces  of  ammonia,  it  is  imperative  to  place  between  the  gas- 
tap  and  the  Pettenkofer  tube  a  Peligot  tube,  charged  with  10 
c.c.  decinormal  acid.  This  last  tube  must  have  ground-in  glass 
connections  ;  any  rubber  connections  up  to  the  absorption  tube 


NAPHTHALENE  301 

should  be  avoided  as  much  as  possible,  as  they  absorb  much 
naphthalene.  Where  they  cannot  be  avoided,  the  ends  of  the 
glass  tubes  must  be  made  to  touch  each  other,  the  connection 
being  made  with  strongly  charged  old  rubber  tube.  The  gas 
is  measured  by  a  meter  behind  the  washing-apparatus ;  it 
should  pass  through  at  the  rate  of  20  to  25  litres  per  hour,  and 
in  the  whole  150  litres  should  be  used.  When  the  experiment 
is  finished,  the  absorbing  liquid  (without  heating  it,  as  pre- 
scribed by  Colman  and  Smith ;  this  is  quite  unnecessary)  is 
separated  from  the  crystallised  picrate  by  filtration  through 
cotton-wool,  and  1 5  c.c.  of  the  filtrate  titrated  with  N/$o  caustic 
potash  and  a  drop  of  methyl  orange  solution.  The  final 
reaction  is  easily  recognised  with  good  light  and  on  a  white 
background,  if  you  look  at  the  drops  as  they  fall  in,  not  at  the 
mixture.  The  standard  of  the  original  absorbing  solution  is 
established  by  titration  in  the  same  manner.  Example : 
Quantity  of  gas  employed,  168  litres ;  titre  of  10  c.c.  picric  acid 
solution  =  21-9  c.c.  of  N/$o  KOH  ;  the  same  of  10  c.c.  filtrate 
after  the  absorption  =15-6  c.c.  N/$o  KOH.  Hence  consumed 
21.9—15.6  =  6-3  c.c.  N/$o  KOH,  and  for  the  15  c.c.  absorbing 
liquid,  6-3x1. 5  =9-45  c.c.  N/$o  KOH.  Since  I  c.c.  =0-00256 

C10H8,  the  100  cb.m.  gas  contain  =^|  x  256=  14-4  g.  C10H8. 

Jorissen  and  Rutten  (/.  Soc.  Chem.  Ind.>  1909,  p.  1179)  point 
out  that  the  process  of  Colman  and  Smith  (supra,  p.  299)  yields 
low  results,  if  too  much  water  is  used  in  washing  the  naphthalene 
picrate  ;  further,  that,  by  employing  a  saturated  solution  of 
picric  acid  containing  also  solid  picric  acid,  the  naphthalene 
picrate  is  directly  precipitated  from  the  gas  as  undissociated 
picrate.  They  proceed  as  follows :  250  c.c.  of  a  saturated 
solution  of  picric  acid  are  evaporated  to  about  150  c.c. 
and  transferred,  while  hot,  to  two  absorption  bottles.  The 
gas,  previously  freed  from  tar  -  fog,  cyanogen,  sulphuretted 
hydrogen  and  ammonia,  is  passed  through  the  bottles  at  the 
rate  of  about  1-5  cb.  ft.  per  hour,  until  a  fair  quantity  of  picrate 
has  been  formed  in  the  first  bottle.  The  solution  and  precipi- 
tate are  then  washed  into  a  flask,  made  up  to  250  c.c.,  the 
closed  flask  heated  to  about  40°  for  about  half  an  hour,  and 
shaken  from  time  to  time  till  all  the  picrate  has  dissolved. 
After  cooling,  the  solution  is  separated  from  the  precipitated 


302  TECHNICAL  GAS-ANALYSIS 

naphthalene  picrate,  and  an  aliquot  portion  of  the  filtrate 
titrated  with  Njio  alkali,  the  same  volume  of  the  original 
solution  being  also  titrated.  From  the  difference  of  the  two 
titrations  the  amount  of  naphthalene  is  readily  calculated  in  a 
similar  manner  to  that  given  above. 

Schlumberger's  description  of  Rutten's  method  in  /. 
Gasbeleucht.,  1912,  p.  1260,  substantially  agrees  with  the  method 
described  by  Pfeiffer  supra;  it  is  there  pointed  out  that  the 
standardising  of  the  picric  acid,  in  lieu  of  alkalimetrical  titration, 
may  be  conveniently  performed  by  a  solution  of  150  g. 
potassium  iodide  and  30  g.  potassium  iodate  in  400  c.c.  water, 
with  starch  solution  as  indicator ;  i  mol.  C10H8  combines  with 
i  mol.  of  picric  acid.  Benzene  vapour  is  not  absorbed  by  cold 
saturated  picric  acid  solution. 

Albrecht  and  Muller  (/.  Gasbeleucht.,  1911,  p.  592)  modify 
the  above-described  method  by  not  evaporating  a  cold  saturated 
picric  acid  solution,  but  preparing  a  saturated  solution  contain- 
ing an  excess  of  solid  acid  by  employing  2-5  picric  acid, 
together  with  a  quantity  of  water  insufficient  for  dissolving  it, 
divided  upon  two  wash-bottles.  When  estimating  the  naphtha- 
lene in  crude  gas,  the  gas  must  not  be  purified  otherwise  than 
by  sulphuric  acid  and  caustic  potash  solution,  since  all  solid 
purifying  agents  retain  naphthalene  and  cause  the  results  to 
be  too  low. 

Pfeiffer  (loc.  cit.^  p.  305),  to  prevent  the  error  caused  by 
naphthalene  being  separated  together  with  the  tar  condensing 
in  the  conduits  before  the  absorbing  apparatus,  proceeds  as 
follows  : — A  f -in.  tap  is  put  in  the  gas-conduit,  through  which 
passes  a  glass  tube,  movable  in  a  rubber  stopper,  one  end  of 
which  enters  freely  in  the  gas-pipe.  The  other,  outer  end  is 
connected  with  a  pipe,  filled  with  cotton-wool  for  retaining  tar- 
fog.  Then  follow  three  Peligot  tubes  with  glass  joints.  The 
first  two  are  charged  each  with  100  to  200  c.c.  of  66  per  cent, 
acetic  acid,  the  last  with  a  concentrated  picric-acid  solution. 
A  gas-meter  follows  in  the  end.  After  passing  about  1 50  litres 
gas  through  the  apparatus  in  five  or  six  hours,  the  whole 
apparatus,  beginning  at  the  gas-conduit  up  to  the  last  Peligot 
tube,  without  taking  it  to  pieces,  is  taken  to  the  laboratory,  in 
order  to  drive  all  the  naphthalene  into  the  absorbing  vessels. 
This  is  done  by  sucking  a  current  of  air  through  the  apparatus 


NAPHTHALENE  303 

and  heating  the  gas-inlet  pipe,  together  with  the  cotton-wool 
filter,  on  a  steam-bath,  whilst  cooling  the  Peligot  tubes  with 
water ;  this  takes  about  an  hour.  Now  the  contents  of  the 
three  Peligot  washers  are  united  and  mixed  with  another  500 
c.c.  concentrated  picric  acid  solution,  whereby  all  the  naphthalene 
is  precipitated  in  flakes.  It  is  filtered  through  an  aspirating 
funnel,  dried  in  vacuo  and  weighed;  i  g.  picrate  =  0-3  585  C10H8. 
In  this  way  Pfeiffer  obtained  from  crude  gas  0-308  g.  picrate  = 
1 10-4  g.  C10H8  in  100  cb.m.  of  gas. 

C.  J.  Dickenson  Gair  (eodom  loco,  1905,  p.  1279;  1907, 
p.  1263)  passes  the  gas  through  two  absorption  bottles 
containing  350  c.c.  of  diluted  acetic  acid  of  sp.  gr.  1-044,  at 
the  rate  of  I  cb.  ft.  per  hour.  At  the  conclusion  of  the  test, 
500  c.c.  of  saturated  picric  acid  solution  are  added,  the  dissolved 
naphthalene  being  thereby  precipitated  as  picrate,  which  is 
filtered  off  on  the  pump,  using  a  dry,  weighed  filter  washed 
with  saturated  picric  acid  solution,  and  finally  once  with 
water.  The  filter-paper  and  precipitate  are  dried  quickly 
in  vacuo  over  sulphuric  acid,  and  weighed.  The  weight  of 

the  naphthalene  picrate  found,  multiplied  by  — 5— •  =0-3585, 

I2o-f-  229 

gives  the  weight  of  naphthalene  in  the  volume  of  gas  passed. 
Or,  the  precipitate  may  be  washed  into  a  flask,  and  titrated  in 
hot  solution  with  Af/io  alkali,  as  previously  described.  In  the 
case  of  cool,  but  unpurified  gas  containing  HCN  and  H2S,  those 
impurities  are  apt  to  affect  the  picric  acid  to  some  extent ;  in 
this  case  the  absorption  by  acetic  acid  is  preferable. 

The  employment  of  alcohol  to  wash  the  naphthalene  from 
the  gas  and  subsequent  precipitation  of  the  solution  with 
aqueous  picric  acid  has  not  proved  successful,  as  under  these 
conditions  some  of  the  other  vapours  present  in  the  gas,  such  as 
the  xylenes,  also  form  crystalline  picrates,  and  too  high  results 
are  therefore  obtained.  Still,  this  process  is  recommended  by 
Ab-der-Halden, /.  Gas  Lighting,  cxx.  p.  230. 

Fronsac  (RJv.  gtn.  de  Mm.,  1914,  p.  4)  describes  a  wash- 
bottle  specially  constructed  for  the  picric  acid  method. 

Laurain  (Bull.  Assoc.  Belg.  des  Chim.,  1912,  No.  i ;  J.  Gas 
Lighting,  1912,  cxviii.  p.  984)  describes  the  method  of  Sainte- 
Claire  Deville  for  separating  the  naphthalene  by  cooling  in  a 
glass  tower  containing  a  copper  spiral,  through  which  circulates 


304  TECHNICAL  GAS-ANALYSIS 

water  of  2°  or  3°  C.  The  naphthalene  condensed  in  the  upper 
part  of  this  tower  is  dissolved  in  alcohol,  precipitated  by  water 
from  the  solution,  filtered,  dried,  and  weighed,  adding  the 
quantity  remaining  in  the  state  of  vapour  at  the  temperature  of 
the  cooling  water.  This  method  is  rather  difficult  to  carry  out 
in  a  satisfactory  manner. 

Another  method,  worked  out  by  Laurain  himself,  ascertains 
the  temperature  at  which  the  naphthalene  separates  from  the 
gas  in  a  solid  form,  and  measures  the  loss  of  pressure  produced 
by  this  secretion,  with  tables  reducing  this  to  the  percentage  of 
naphthalene. 

Lebeau  and  Damiens,  in  a  number  of  communications  made 
in  1913  (Comptes  rend.,  clvi.  and  clvii.),  describe  their  methods 
for  the  examination  of  hydrocarbon  mixtures  by  the  application 
of  low  temperatures. 

The  Societ^  du  Gaz  de  Paris  (Ger.  P.  266154)  estimates  the 
percentage  of  naphthalene  in  illuminating  gas  by  the  tempera- 
ture of  saturation  of  the  naphthalene  vapour,  by  means  of  an 
apparatus  provided  with  a  contrivance  for  regulating  and 
measuring  the  temperature,  consisting  in  a  narrow  orifice  in 
the  gas-pipe,  in  which  a  differential  manometer  measures  the 
diminution  of  pressure.  The  gas  is  introduced  at  the  ordinary 
temperature,  so  that  the  thermometer  shows  the  temperature  at 
which  in  the  orifice  (which  may  be  still  further  narrowed  by  an 
artificial  deposition  of  naphthalene)  no  naphthalene  is  either 
precipitated  or  evaporated. 

TOTAL  HEAVY  HYDROCARBONS  IN  COAL-GAS. 

Their  estimation  by  absorption  in  concentrated  sulphuric 
acid  or  bromine  water  has  been  described  supra,  pp.  uSand 
1 19).  Hempel  and  Dennis  (Ber.,  1891,  p.  1 162)  pass  the  gas  first 
into  a  Hempel  burette  where  it  is  measured,  and  from  this  into 
a  gas-pipette  filled  with  mercury,  say  an  "explosion-pipette  "(pp. 
90  and  156),  where  it  is  shaken  up  for  three  minutes  with  i  c.c. 
of  absolute  alcohol,  which  takes  out  all  the  hydrocarbon  vapours. 
The  gas  is  carried  back  into  the  burette,  and  from  this,  in  order 
to  remove  the  alcohol  vapour,  into  a  second  mercury  pipette, 
where  it  is  shaken  up  with  i  c.c.  of  water  for  three  minutes,  after 
which  the  contraction  of  volume  is  noted.  Both  alcohol  and  water 


TAR  VAPOURS  305 

should  first  be  saturated  with  coal-gas  to  prevent  methane,  carbon 
monoxide  and  nitrogen  from  being  dissolved,  as  specially  pointed 
out  by  F.  Fischer  (Z.  angew.  Chem.^  1897,  p.  351). 

Bujard  (Z.  angew.  Chem.,  1897,  p.  45)  recommends  this 
method,  both  for  coal-gas  (for  which  he  also  employs  I  c.c. 
alcohol)  and  for  "  air-gas,"  for  which  4  or  5  c.c.  alcohol  should  be 
taken.  . 

Merriam  and  Birchby  (/".  Ind.  and  Eng.  Chem.,  1913,  p.  822) 
describe  their  empirical  tests  for  approximately  determining  the 
quantity  of  gasoline  obtainable  from  natural  gas,  viz.,  absorption 
by  kerosene  and  by  olive  oil.  They  got  the  best  results  by 
compressing  the  gas  in  a  compressor  constructed  by  them. 

James  G.  Vail  (/.  Ind.  and  Eng.  Chem.,  1913,  p.  756)  estimates 
the  hydrocarbons  in  coal-gas,  after  absorbing  CO2,  CO,  and  O, 
by  explosion  with  a  mixture  of  O  and  N,  prepared  in  the 
pipette  itself  by  the  electrolysis  of  water  acidulated  with 
sulphuric  acid. 

TAR  VAPOURS. 

Most  of  the  tar  produced  in  the  distillation  of  coal  is  con- 
densed to  a  liquid  already  in  the  hydraulic  main  in  the 
condensers,  and  the  Pelouze  or  Livesey  apparatus,  specially 
constructed  for  this  purpose.  Still,  even  in  the  normal  working 
of  the  best  apparatus,  the  finest  tar-fog  is  carried  forward  by  the 
gas  ;  it  passes  partly  through  the  scrubbers,  and  almost  the  last 
traces  of  it  are  ultimately  retained  in  the  oxide-of-iron,  purify- 
ing mass,  owing  to  its  filtering  action.  This  is  certainly  not  the 
proper  object  of  that  mass,  which  by  its  becoming  soaked  with 
tar  is  prematurely  rendered  useless  for  its  proper  task  in  the 
manufacture  of  gas,  and,  moreover,  later  on  causes  great  trouble 
in  working  the  mass  for  cyanides,  etc.  The  crude  gas  ought  to 
be  freed  from  tar  as  much  as  possible  in  the  condensers  and 
scrubbers  before  it  goes  into  the  purifiers.  Hence  the  examina- 
tion of  the  crude  gas  for  its  contents  of  tar  in  that  particular 
place  gives  valuable  information  on  the  working  of  the  process. 
The  street  gas  also  always  contains  traces  of  tar  vapours,  which 
impart  to  it  its  specific  smell ;  but  these  traces  are  so  slight  that 
they  cannot  be  supposed  to  do  any  harm,  and  therefore  they 
need  not  be  specially  enquired  into.  To  be  sure  Freitag  (/"., 
Gasbeleucht.,  1870,  p.  33)  attributes  the  damage  done  to  plants 

U 


306 


TECHNICAL  GAS-ANALYSIS 


in  the  case  of  gas  issuing  from  leaks  in  the  gas-pipes,  just  to 
the  tar  vapours;  cf.  also  Pfeiffer  (ibid.y  1898,  p.  137). 

The  qualitative  proof  for  the  presence  of  tar  vapour  in  crude 
gas  is  generally  made  by  placing  a  piece  of  white  paper  against 
the  gas  issuing  from  a  small  orifice.  The  place  struck  by  the 
gas  in  front  of  the  scrubbers  at  once  turns  brown  or  black, 
behind  the  washer  only  after  some  time.  • 

In  street  gas  any  tar  present  can  be  proved  by  a  solution  of 
a  small  crystal  of  diazobenzene-sulphuric  acid,  dissolved  in 
10  c.c.  water  (Pfeiffer,  in  Lunge-BerPs  Chemisch-technische 
Untersuchungsmethoden,  iii.  p.  307). 

The  quantitative  estimation  of  tar-fog  in  the  gas  is  carried 
out  by  various  methods. 

i.  Tieftrunk's  apparatus  (Fig.  121)  causes  the  gas  to  pass 


FIG.  121. 

through  spirit  of  wine  which  mechanically  retains  the  tar ;  the 
latter  is  estimated  by  filtration  and  drying.  The  absorbing- 
cylinder  a  is  provided  at  the  top  with  a  brass  flange,  with  which 
the  ground-up  brass  cover  b,  greased  with  a  little  tallow,  is 
connected  air-tight  by  the  screw  clamps  k,  k.  The  gas  goes  in 
through  pipe  e,  which  is  continued  by  means  of  rubber  tubes  with 
tube  gy  reading  nearly  down  to  the  bottom  of  a.  Tube  ^carries  six 
loosely  put  on  brass  bells,  perforated  with  a  number  of  1-5  mm. 
holes,  in  distances  of  5  mm.  Alcohol  of  30  to  35  vols.  per  cent, 
is  put  into  a  so  far  that  all  the  bells  are  covered.  On  the  gas 
passing  through  the  holes,  the  tar-fog  is  mechanically  retained, 


TAR  VAPOURS  307 

and  the  last  traces  of  it  are  kept  back  by  the  cotton-wool, 
loosely  filling  the  U-tube/  The  tubulated  bottle  now  follow- 
ing contains  at  the  bottom  a  layer  of  India  fibre  o,  above  this  a 
disc  of  filtering-paper,  and  on  this  a  layer  of  bog-iron  ore 
purify  ing- mass,  intended  to  retain  the  sulphuretted  hydrogen 
which  would  damage  the  meter.  The  gas  gets  out  through  />,  its 
propulsion  through  the  apparatus  being  produced  by  a  water- 
jet  pump. 

This  apparatus,  if  possible,  is  placed  close  to  the  orifice  for 
the  gas  ;  if  this  is  not  possible,  it  is  connected  with  it  by  a  tared 
glass  pipe,  inclined  towards  the  apparatus,  which  is  reweighed 
after  finishing  the  test  In  front  of  the  condensers,  250  litres 
gas  are  drawn  through  the  apparatus  with  a  velocity  of  30  to  40 
litres  per  hour ;  in  front  of  and  behind  the  scrubbers  500  litres 
with  a  velocity  of  50  to  60  litres  per  hour. 

After  finishing  the  passage  of  gas,  cover  b  is  removed,  the 
tar  adhering  to  the  bells  washed  off  with  alcohol  of  30  to  35 
vols.  per  cent.,  and  the  washings  poured  to  the  liquid  remaining 
in  the  vessel.  After  twelve  hours'  settling,  the  liquid  is  passed 
through  a  dry,  weighed  filter  by  the  aid  of  an  air-pump,  which 
is  stopped  as  soon  as  the  tar  gets  on  to  the  filter.  The  alcoholic 
liquid  is  allowed  to  drain  off,  the  filter  and  contents  are  put  into 
a  tared  glass  dish,  which  is  placed  into  a  desiccator  for  twelve 
hours  and  weighed.  The  cotton-wool  in  tube/,  if  coloured,  is 
washed  with  carbon  disulphide.  The  filtrate  is  allowed  to  drop 
into  a  tared  glass  dish,  which  is  dried  at  the  ordinary  tempera- 
ture in  a  current  of  air.  The  weight  of  the  remaining  tar  is 
added  to  that  found  before.  Since  a  little  tar  has  remained  in 
the  bottle  a  and  on  the  bells,  dry  air  is  sucked  through  the  bottle 
until  all  the  moisture  has  vanished,  and  the  increase  of  weight  of 
the  (previously  weighed)  apparatus  is  noticed.  The  balance 
used  must,  when  weighed  with  i  kg.,  indicate  ooi  g.  The 
results  are  noted  in  terms  of  kilograms  tar  per  1000  cb.m.  gas. 
In  that  quantity,  150  to  200  kg.  tar  are  found  in  front  of  the 
coolers,  25  to  75  kg.  in  front  of  the  scrubbers,  0-5  to  20  kg.  in 
front  of  the  purifiers. 

Tieftrunk's  method   is  very  strongly  criticised  by  Feld,  in 
his  paper  quoted  below,  as  yielding  quite  unreliable  results. 

2.  Clayton  and  Skirrow  (/.  Gas  Lighting,  1907,  p.  660)  retain 
the  tar-fog  by  a  cotton-wool  filter.     A  long  glass    tube,  J  in. 


308  TECHNICAL  GAS-ANALYSIS 

in  external  diameter,  has  a  small  hole,  \  in.  diameter.  Down 
near  one  end,  and  about  12  in.  of  the  tube  above  this 
hole  is  filled  with  loosely  packed  cotton-wool,  which  has  been 
previously  extracted  with  carbon  disulphide  to  remove  fatty 
matter.  The  end  of  the  tube  near  the  small  side  hole  is  closed 
by  a  cork ;  the  tube  inserted  through  a  cork  is  placed  in  a  ij-in. 
cock  on  the  gas  main,  and  so  fixed  that  the  small  side  hole  faces 
the  gas  stream  as  nearly  as  possible  two-thirds  across  the  main, 
or  one-third  of  the  diameter  from  the  side  opposite  to  the  cock 
through  which  it  is  inserted,  this  being  the  point  of  mean  velocity 
of  gas  in  the  main.  The  whole  of  the  filtering  material  should  be 
within  the  main,  so  that  it  is  kept  at  the  same  temperature  as 
the  gas  to  avoid  condensation,  and  the  gas  is  allowed  to  pass 
through  the  filter  at  such  a  rate  that  its  velocity  through  the 
J-in.  hole  is  greater  than  that  of  the  gas  in  the  main.  Only 
by  observing  these  precautions  uniform  results  can  be  obtained. 
After  passing  the  filter,  the  gas  is  purified  from  sulphuretted 
hydrogen  by  oxide  of  iron,  and  measured  in  a  meter,  from  20  to 
30  cb.  ft.  being  employed.  The  tube  is  then  removed  from 
the  main,  the  external  surface  wiped  clean  from  tar,  and  the 
cotton-wool  containing  the  tar  placed  in  a  Soxhlet  tube  and 
extracted  with  carbon  disulphide  in  a  tared  flask.  The  CS2- 
extract  is  evaporated  on  a  water-bath,  dry  air  finally  drawn 
through  the  flask  for  half  a  minute,  and  the  flask  again  weighed. 
From  the  weight  of  tar  and  the  volume  of  gas  passed,  the 
amount  of  tar-fog  per  I  or  100  cb.  ft.  of  gas  is  readily  calculated. 
The  free  carbon  of  the  tar  remains  undissolved  in  the  cotton- 
wool, and  some  of  the  low-boiling  constituents  of  the  tar  are 
evaporated  with  the  carbon  disulphide,  so  that  the  results  are 
below  the  exact  figure  ;  but  the  figures  obtained  are  fairly  com- 
parative and  sufficiently  exact  for  most  practical  purposes. 

Feld  (/.  Gasbeleucht.)  1911,  p.  33)  tries  to  avoid  the  just- 
mentioned  errors  of  this  method  in  the  following  manner  : — The 
gas  drawn  from  the  main  is  passed  through  a  weighed  |J-tube 
containing  cotton-wool.  Before  weighing,  the  latter  is  placed 
in  a  water-bath  warmed  to  the  temperature  of  the  gas  in  the 
main,  and  the  gas  passed  through  it,  after  traversing  two 
additional  U-tut>es  placed  in  the  same  bath  and  filled  with 
cotton-wool  (unweighed)  and  calcium  chloride  respectively,  until 
its  weight  is  constant.  The  tube  is  then  connected  directly 


INFLAMMABLE  GASES  309 

with  the  tar-laden  gas  stream,  and  a  measured  volume  of  gas 
passed  through  it.  It  is  then  reconnected  to  the  outlet  of  the 
two  U~tuDes  previously  employed,  and  the  gas  again  passed 
until  the  weight  of  the  tar  absorption  tube  is  constant ;  the 
increase  of  weight  gives  the  amount  of  tar-fog  in  the  volume  of 
gas  passed.  Working  in  this  manner,  the  moisture  in  the 
filtered  tar  is  removed  without  simultaneous  loss  of  tar  vapours, 
as  the  gas  is  always  saturated  with  tar  vapours  at  the 
temperature  of  the  water  in  the  bath  and  in  the  gas  main.  By 
lowering  the  temperature  of  the  bath,  the  lowering  of  the  tar 
contents  of  the  gas  for  any  interval  of  temperature  can  be 
determined. 

Gwiggner  (fhem.  Zeit.,  1912,  p.  461)  retains  the  tar  by  a  slag- 
wool  filter. 

Jenkner  (Stahl  u.  Eisen,  xxxii.  p.  1 129  ;  Chem.  Centr.,  1912,  ii. 
p.  1498)  describes  an  apparatus  for  discovering  tar,  ammonia,  and 
benzene  in  coke-oven  gases,  in  which  the  tarry  constituents 
are  retained  on  a  cotton-wool  filter,  heated  to  65°  to  70°  by 
electrical  means.  The  ammonia  is  removed  by  blowing  pre- 
heated air  through  the  filter. 


DETECTION  OF  INFLAMMABLE  GASES  AND  VAPOURS 

IN   THE   AlR.1 

In  some  cases  the  air  contained  in  a  closed  space,  e.g.,  in  the 
bunkers  of  coal-ships,  benzene  tanks,  oil-ships,  etc.,  should  be 
regularly  tested  for  the  presence  of  inflammable  gases  and 
vapours.  For  this  purpose  an  automatically  acting  apparatus 
has  been  constructed  by  Philip  and  Steele  (/.  Soc.  Chem.  Ind.t 
1911,  p.  867)  which  depends,  like  some  others  previously 
devised,  upon  the  catalytic  action  of  heated  platinum  surfaces 
to  secure  the  combustion  of  mixtures  of  oxygen  and  combustible 
gas  or  vapour  which  may  be  passed  through  it ;  but,  differently 
from  its  predecessors,  is  so  arranged  that  it  is  completely 
guarded  against  any  danger  of  overheating  whatever  the 
proportion  and  nature  of  the  mixture  of  combustible  gas  and 
vapour  with  air  may  be. 

1  Cf.  Lunge- Keane's  Technical  Methods,  i.  pp.  896  et  seq.>  and  supra,  p. 
152. 


310  TECHNICAL  GAS-ANALYSIS 

Their  detector,  Fig.  122,  consists  of  two  coils  of  platinum 
wire,  CL  and  C2,  of  approximately  the  same  resistance  and 
arranged  parallel  with  one  another.  In  series  with  each  of 
them  is  one  of  the  coils  of  a  differential  galvanometer,  Gl  and 
G2,  in  fact,  a  relay.  The  armature  or  relay  tongue  t  (Fig.  123) 
of  this  relay  is  capable  of  being  moved  by  a  very  small  strength 
of  the  current  flowing  in  either  of  its  coils.  The  two  platinum 
coils  of  the  detector  are  enclosed  in  glass  tubes,  and  the  gas 


FIG.  122. 

which  is  to  be  examined  is  pumped  over  the  outside  of  one  of 
these  tubes  enclosing  the  coil  C2,  without  coming  into  contact 
with  the  platinum  wire.  The  gas  current  then  passes  on  to  the 
second  glass  tube  inside  which  it  flows,  and  is  thus  brought 
directly  into  contact  with  the  hot  platinum  coil  Cr  Connected 
in  series  between  each  of  the  platinum  wire  coils,  Cx  and  C2, 
and  the  coils  of  the  relay,  Gl  and  G2,  to  which  they  are  joined, 
is  a  small  low-resistance  annunciator  coil.  These  two  coils  are 
marked  Al  and  A2  in  Fig.  122.  When  the  switch  of  the 
apparatus  is  closed,  they  indicate  visually  whether  the  currents 


INFLAMMABLE  GASES 


311 


are  actually  passing  through  both  of  the  platinum  coils.  In  the 
event  of  either  of  these  being  fused  or  broken,  the  corresponding 
annunciator  shows  a  red  spot,  marked  "  right "  or  "  left-hand 
platinum  coil  fused."  On  the  other  hand,  if  the  coils  are 
carrying  the  correct  currents,  each  annunciator  shows  the 
letters  O.K. 

The  electric  currents  of  the  relay,  which  are  quite  separate 
from   those   of  the   electric   coil   circuit,   are   for   the   sake   of 


FIG.  123. 

simplicity  not  shown  in  Fig.  122,  but  are  shown  separately  in  a 
diagrammatic  form  in  Fig.  123.  In  this  diagram  the  relay 
tongue  t  moves  between  two  stops  Sx  and  S2,  and  is  itself 
connected  to  a  point  between  two  electric  incandescent  carbon 
filament  lamps,  marked  R  and  W.  These  two  lamps  are 
arranged  in  series  across  the  supply  mains  to  which  the  detector 
is  connected.  One  lamp,  R,  is  contained  in  a  red  glass,  and 
the  other,  W,  in  a  colourless  glass  shade.  It  is  evident  that 
when  the  relay  tongue  is  against  either  of  the  stops  Si  or  S2, 
the  corresponding  lamp  is  short-circuited  through  the  stop  and 
relay  tongue,  and  is  therefore  extinguished,  whilst  the  other 
lamp  has  the  full  voltage  of  the  supply  mains  on  it,  and  is 
consequently  burning  at  full  brightness.  In  the  diagram,  Fig. 
123,  the  red  light  R  is  short-circuited,  and  the  white  lamp  W 
is  lighted.  This  is  the  normal  condition  of  the  detector  when 
connected  to  the  mains,  if  the  air  under  test  contains  no 
inflammable  gas  or  vapour, 


312  TECHNICAL  GAS-ANALYSIS 

Let  us  suppose  that  the  instrument  is  connected  to  the 
mains,  then  a  current  of  electricity  flows  through  the  series  of 
coils  Cx,  Av  Gl  (Fig.  122),  and  another  of  approximately  the 
same  strength  through  the  series  C2,  A2,  G2.  If  the  relay  tongue 
is  then  properly  adjusted  for  these  particular  current  strengths, 
it  will  rest  as  shown  in  Fig.  123,  so  that  the  white  lamp  W  is 
burning  and  the  red  lamp  R  is  extinguished,  whilst  the 
annunciators  Ax  and  A2  will  show  O.K.  The  current  passing 
through  the  coils  Q  and  C2  is  so  strong  that  they  scorch  paper 
held  against  them,  whilst  both  the  annunciator  coils  A1  and  A2, 
and  the  relay  coils  G1  and  G2  are  of  so  low  a  resistance  that  the 
same  currents  passing  through  them  do  not  sensibly  warm  them. 

As  all  the  currents  are  in  parallel  across  the  supply  mains, 
directly  the  current  is  switched  on  to  the  instrument,  a  current 
of  air  is  pumped  over  the  hot  platinum  coils.  In  the  absence  of 
combustible  gas  or  vapour,  the  white  lamp  remains  lighted, 
whilst  the  red  lamp,  being  short-circuited,  shows  no  light.  If 
the  air  passing  through  the  instrument  becomes  contaminated 
with  a  combustible  gas  or  vapour,  the  temperature  of  the 
platinum  coil  C2  remains  unaffected,  as  the  air  does  not  come 
directly  into  contact  with  it.  It  does,  however,  come  into 
contact  with  coil  Cx,  and  as  the  combustible  material  burns  by 
the  catalytic  action  of  the  surface  of  the  hot  platinum,  it  further 
heats  the  wire  to  a  degree  corresponding  with  the  amount  of 
inflammable  gas  or  vapour  in  the  air.  Owing  to  this,  the 
resistance  of  coil  Cx  rises,  and  this  causes  a  diminution  of  the 
current  flowing  through  the  relay  Gr  This  causes  the  release 
of  the  relay  tongue,  and  it  therefore  swings  against  the  other 
stop  S2.  This  action  breaks  the  short  circuit  of  the  red  lamp, 
which  becomes  lighted,  whilst  the  white  lamp  is  at  the  same 
time  short-circuited  and  thus  extinguished,  and  by  this  means 
a  visual  signal  is  given  that  a  definite  percentage  of  inflammable 
gas  or  vapour  is  present  in  the  air  under  test.  In  parallel  with 
the  red  signal  lamp  and  with  one  another  are  arranged  two 
other  circuits,  viz.,  a  single-stroke  electric  bell  B,  and  secondly, 
a  valve-coil  V.  These,  however,  may  be  arranged  as  in  the 
instrument  shown  here  in  series  with  each  other,  and  in  parallel 
with  the  red  signalling  lamp.  The  bell  coil  may  be  installed 
at  any  suitable  distant  point.  The  valve  coil  actuates  a  gas 
cut-off  valve. 


FERROCARBONYL  313 

The  original  communication  contains  a  number  of  further 
devices  for  making  the  action  of  the  instrument  safe  and  more 
sensitive.  It  was  testified  in  the  discussion  following  the 
reading  of  this  paper  that  the  instrument  was  doing  very 
good  service,  and  retained  its  efficiency  for  years. 

Various  patents  of  the  same  inventors  (B.  Ps.  27281  of  1911  ; 
1469  and  15667  of  1912  ;  3002,  4003,  and  4004  of  1913)  contain 
improvements  in  details. 

A  similar  method  is  described  by  Harger  (J.  Soc.  Chem.  Ind.t 
1913,  p.  460). 

Another  instrument  for  the  same  object  is  that  described 
in  the  French  patents  of  Guasco,  437585,  and  his  Ger. 
P-  259337-  A  Leslie  differential  thermometer  is  used, 
one  bulb  being  coated  with  catalytic  metal  or  alloy.  Should 
inflammable  gas  be  present  in  the  air,  its  combustion,  induced 
by  the  catalytic  metal  raises  the  temperature  of  the  bulb. 
The  thermometer  stem  is  graduated  empirically  to  represent 
certain  conditions  of  the  atmosphere.  In  another  form  of 
the  apparatus,  wires  are  sealed  into  the  stem  of  the  thermo- 
meter, and  the  rise  of  the  mercury  brings  about  a  contact  and 
rings  a  bell. 

On  the  same  principle  is  founded  the  apparatus  of  Felser 
(Ger.  P.  266046). 

An  apparatus  for  indicating  the  presence  of  detonating 
gases  in  the  air  of  pits,  etc.,  is  described  in  H.  Neubaur's  Fr.  P. 
452992;  another  in  Philip  and  Steele's  B.  P.  5467  of  1913 
and  in  Hobel's  Ger.  P.  270809. 

W.  Baxter  (B.  P.  27264  of  1912)  describes  an  apparatus 
for  testing  gases  with  miners'  safety  lamps. 

FerrocarbonyL 

This  compound  occurs  in  slight  quantities  in  water-gas ; 
Roscoe  and  Scudder  found  in  I  cb.m.  of  such  gas  2-40  g.  Fe 
which  must  have  been  present  therein  in  the  form  of  FeCO. 
It  is  estimated  by  passing  a  measured  volume  of  water-gas 
through  a  refractory  glass  tube,  heated  to  red  heat ;  it  is 
thereby  decomposed  into  CO  and  metallic  iron,  which  is  partly 
deposited  in  the  tube  as  a  dark  mirror.  Another  portion  of 
the  iron  is  carried  away  by  the  gaseous  current  in  the  shape 


314  TECHNICAL  GAS-ANALYSIS 

of  dust,  and  can  be  retained  by  a  cotton-wool  plug,  placed  in 
the  end  of  the  tube.     The  iron  deposited  in  both  places   is 
dissolved  in  dilute  sulphuric  acid  and  estimated  by  titration. 
Nickel  carbonyl  might  be  estimated  in  a  similar  manner. 

Nitroglycerine. 

This  compound  may  be  carried  into  the  air  in  the  shape 
of  fog  found  in  blasting  operations.  Although  its  quantity 
will  be  in  any  case  very  slight,  it  causes  even  then  headaches 
and  other  troubles,  and  its  estimation  may  be  desirable.  This 
can  be  effected  by  agitating  a  measured  volume  of  the  air 
with  alcohol  which  absorbs  the  nitroglycerin ;  the  latter  can 
be  estimated  by  evaporating  the  alcohol  at  the  ordinary 
temperature. 

The  analysis  of  nitroglycerine  itself  does  not  belong  to 
the  domain  of  gas-analysis;  we  will  only  mention  that  it  is 
carried  out  by  means  of  Lunge's  nitrometer  or  gas-volumeter 
(supra,  pp.  2 1  et  seq). 

Nitrogen  Protoxide  (Nitrous  Oxide\  N2O. 

This  compound  occurs,  e.g.y  in  vitriol-chamber  gases,  and 
its  estimation  may  be  desirable  in  order  to  establish  what  loss 
of  "nitre"  is  thereby  caused  in  the  sulphuric  acid  manu- 
facture. It  is  pretty  freely  soluble  in  water  ;  Bunsen  expresses 
this  solubility  by  the  formula  : 

1-3052  —  0-045362/4- 0-0006843^. 
Pollak,  as  quoted  by  Treadwell  (Lehrbuch,  ii.  p.  565)  found  it 

=  1-13719  -  0-042265/4-  o«ooo6io/2. 

Its    solubility   in   alcohol   is    even    more   considerable,   about 
thrice  the  figure  for  water. 

We  do  not  as  yet  possess  any  method  for  the  qualitative 
detection  of  small  amounts  of  this  gas.  Its  quantitative  estima- 
tion may  be  performed  by  combustion  in  various  ways. 

Winkler  (Technical  Gas- Analysis,  p.  164)  proposed  mixing 
the  gas  with  hydrogen  and  passing  this  mixture  through 
platinum  asbestos,  contained  in"  a  moderately  heated  tube, 
thus  producing  the  reaction  : 

2  =  N2  +  H20, 


NITROGEN  PROTOXIDE  315 

Hence  2  vols.  N2O  +  2  vols.  H  furnish  2  vols.  N2  (the  H2O 
being  condensed  to  liquid  water),  and  the  contraction  produced 
by  combustion  directly  indicates  the  volume  of  nitrogen 
protoxide.  But  this  method  is  only  applicable  to  gases 
containing  no  other  constituents  acting  upon  hydrogen,  such 
as  oxygen,  nitric  oxide,  etc.,  and  is  therefore  useless  for 
most  practical  cases;  certainly  in  the  (most  usual)  case  where 
the  proportion  of  N2O  in  the  gaseous  mixture  is  only  very 
slight,  especially  as  it  involves  the  previous  removal  of  the 
oxygen  and  the  nitrogen  acids  and  nitric  oxide  from  the 
gas.  The  same  must  be  said  of  the  method  of  Bunsen,  who 
effects  the  combination  of  nitrogen  protoxide  with  hydrogen 
by  explosion. 

Dumreicher  (Wiener  Akadem.  Ber.^  1881,  p.  560)  burns  the 
gas  with  hydrogen  in  an  endiometer.  Hempel  (Berl.  Ber.,  1881, 
p.  903 ;  Z.  Elektrochem.,  1906,  p.  200)  uses  the  same  method  in 
his  explosion  pipette,  employing  two  or  three  times  the  volume 
of  hydrogen,  and  adding  so  much  oxyhydrogen  gas  as  will 
give  26  to  64  vols.  of  combustible  gas  to  every  100  vols.  of 
incombustible  gas. 

Knorre  and  Arendt  (Berl.  Ber.,  1899,  p.  2136;  1900,  p.  30) 
pass  a  mixture  of  nitrous  oxide  and  hydrogen  slowly  through 
a  red-hot  Drehschmidt  capillary  (vide  supra,  p.  100). 

Pollak  (as  communicated  by  Treadwell,  in  whose  laboratory 
the  process  was  worked  out)  also  tried  hydrogen,  but  he  found 
it  preferable  to  employ  carbon  monoxide.  The  gas,  previously 
freed  from  oxygen  by  passing  over  moist  phosphorus,  is  mixed 
with  carbon  monoxide,  and  passed  over  platinum  contained  in 
a  Drehschmidt  capillary  tube  (p.  100).  The  carbon  dioxide 
formed  is  determined  in  the  usual  way  ;  its  volume  is  equal  to 
that  of  the  N2O  originally  present : 


N2O  +  CO=  CG2-r^2. 

2  vols.    2  vols.       2  vols.    2  vols. 

A  method  for  estimating  very  small  quantities  of  nitrogen 
protoxide  in  the  exit  gases  from  the  vitriol  chambers,  worked 
out  by  Inglis,  will  be  described  infra. 

A  method  proposed  by  myself  (Lunge,  Ber.,  1881,  p.  2188), 
founded  upon  the  considerable  solubility  of  nitrogen  protoxide 
in  alcohol,  and  decomposing  the  gases  expelled  from  the  latter 


316  TECHNICAL  GAS-ANALYSIS 

into  N   and   O  by  glowing   palladium    wire,  is  not  very  well 
adapted  for  the  estimation  of  very  slight  percentages  of  N2O. 

According  to  Baskerville  and  Stevenson  (/.  Ind.  Eng. 
Cfom.,i9ii,p.  579),  none  of  the  well-known  methods  for  the 
determination  of  nitrogen  protoxide  in  a  gaseous  mixture  of 
which  it  is  the  principal  constituent  is  quite  satisfactory. 
Explosion  with  hydrogen  may  lead  to  results  fully  2  per  cent, 
below  the  truth,  far  too  large  an  error  when  the  object  of 
analysis  is  to  compare  two  commercial  brands  of  compressed 
gas,  of  which  few  contain  less  than  95  per  cent,  and  some  over 
99  per  cent,  of  N2O.  Exact  results  may  be  obtained  by  the 
following  indirect  method  :  A  measured  volume  of  the  gas  is 
passed  over  ignited  copper  gauze  previously  reduced  in  a 
current  of  hydrogen,  and  the  current  of  gas  is  followed  by  one 
of  hydrogen,  the  water  formed  during  this  stage  of  the 
experiment  being  collected  in  a  tared  drying-tube.  The 
method,  of  course,  indicates  not  nitrogen  protoxide  alone, 
but  also  any  oxygen,  free  and  combined,  contained  in  the 
gas.  In  practice,  however,  the  only  correction  usually  necessary 
is  that  for  the  moisture  of  the  gas,  since  commercial  nitrogen 
protoxide  appears  to  be  free  from  compounds  of  oxygen  other 
than  N2O,  and  although  oxygen  can  be  detected  in  nearly 
every  sample,  its  amount  seems  never  to  reach  o  i  per  cent. 

Nitric  Oxide,  NO. 

Qualitative  Detection. — This  can  be  performed  by  oxidising 
the  NO  by  means  of  atmospheric  oxygen,  or  otherwise,  whereby 
nitrogen  peroxide  is  formed,  and  passing  the  gases  through  a 
dilute  solution  of  sodium  or  potassium  hydrate,  which  then 
contains  alkaline  nitrates  and  nitrites.  The  presence  of  the 
latter,  and  thereby  the  original  presence  of  NO,  is  proved  by 
acidifying  the  solution  with  acetic  acid  and  adding  the  reagent 
of  Griess,  on  a-naphtylamine  and  sulphanilic  acid,  as  improved 
by  Lunge.  The  reagent  is  prepared  as  follows :  Dissolve 
0-5  g.  of  a-naphtylamine  in  20  c.c.  boiling  water,  pour  off 
the  colourless  solution  from  the  violet  residue,  and  add  to  the 
solution  150  c.c.  of  dilute  acetic  acid.  On  the  other  hand, 
dissolve  0-5  g.  of  sulphanilic  acid  in  150  c.c.  of  dilute  acetic 
acid.  Mix  the  two  solutions  and  keep  them  in  a  tightly 


NITRIC  OXIDE  317 

stoppered  bottle.  The  reagent  should  be  kept  in  the  dark 
when  not  in  use.  For  making  the  test  heat  the  absorbent, 
which  may  now  contain  some  nitrite,  to  about  80°,  and  add 
about  one-fifth  of  its  volume  of  the  Griess  reagent.  If  nitric 
oxide  had  been  present  in  the  original  gas  mixture,  a  red 
colour  is  produced.  The  reaction  is  extremely  delicate,  i 
part  of  nitrous  acid  in  1000  million  parts  of  the  solution  pro- 
ducing a  distinct  red  colour  after  one  minute. 

Quantitative  Estimation  of  Nitric  Oxide. — This  has  been 
mentioned  in  several  previous  places. 

I.  By  Absorbing  Agents ',  vide  p.  128. 

II.  Oxidation  to  Nitric  Acid. — This  may  be  brought  about 
by  passing  the  gaseous  mixture  through  absorbing  bottles,  or  a 
ten-bulb   absorption   tube  (Fig.    72,  p.   146)  or   other   efficient 
apparatus   containing  an  oxidising  solution.     As  such  may  be 
used  a  seminormal  solution  of  potassium    permanganate,  say 
30  c.c.,  to  which   I   c.c.  of  sulphuric  acid,  specific  gravity  1-8,  is 
added.     After   passing  a  sufficient  quantity  of  gas  by  means 
of  an  aspirator  through  this  solution,  the  solution  is  titrated, 
preferably  by  adding  a  solution  of  ferrous  sulphate,  the  relation 
of  which  to   the  permanganate  has  been  ascertained,  and    re- 
titrating  with  permanganate  till  the  rose  colour  reappears.    Each 
cubic  centimetre  of  permanganate  consumed  indicates  0-007  g. 
N  in  the  shape  of  NO,  or  0-10803  grains  N  per  cubic  foot. 

Von  Knorre  (Chem.  Ind.^  1902,  p.  534)  in  the  case  of  large 
quantities  prefers  absorbing  the  NO  in  a  mixture  of  5  vols. 
of  saturated  potassium  bichromate  solution  and  I  vol.  concen- 
trated sulphuric  acid,  which  is  perfectly  stable  at  ordinary 
temperatures,  and  does  not  evolve  oxygen  when  agitated  with 
indifferent  gases,  whilst  oxidising  the  NO  quantitatively  to 
HN03. 

Divers  (/.  Chem.  Soc.,  1899,  Ixxv.  p.  82)  employs  for 
absorbing  the  nitric  oxide  a  concentrated  alkaline  solution  of 
sodium  or  potassium  sulphite,  whereby  hyponitrososulphate, 
NaN2O2SO3,  is  formed.  Any  carbon  dioxide  or  other  acid 
gas  present  along  with  the  nitric  oxide  must  be  previously 
removed  by  alkali. 

Schonbein  (/.  prakt.  Chem^  1860,  p.  265)  found  that 
nitric  oxide  is  oxidised  to  nitric  acid  by  an  excess  of 
hydrogen  dioxide,  and  this  reaction  has  been  tried  by  various 


318  TECHNICAL  GAS-ANALYSIS 

chemists  for  its  quantitative  estimation,  e.g.,  by  myself  (Z. 
angew.  Chem.,  1890,  p.  568),  but  I  discarded  it  as  not 
sufficiently  accurate.  Moser  (Z.  anal.  Chem.,  1911,  p.  401) 
states  that  the  NO  can  be  completely  absorbed  in  six  to 
twelve  minutes  when  employing  an  absorption  bulb  designed 
by  him  (vide  infrd). 

III.  Combustion  of  NO  by  Atmospheric  Air  in  the  Presence  of 
Potassium  Hydrate.  —  Baudisch  and  Klinger  (Berl.  Ber.,  1912,  p. 
3231)  pass  atmospheric  air  into  the  gas  containing  NO,  stand- 
ing over  sticks  of  caustic  potash  in  a  gas-pipette.  The  NO  is 
oxidised  into  N2O3  which  is  momentarily  taken  up  by  the  KOH, 
so  that  the  formation  of  any  NO2  is  completely  excluded. 

The  reactions  are  : 


(i)  4NO  +  02  =  2N20 
(2) 


Hence  4  vols.  of  nitric  oxide  absorb  I  vol.  oxygen  ;  therefore 
four-fifths  of  the  contraction  observed  when  passing  air  into  the 
pipette  containing  NO  in  contact  with  moistened  caustic  potash 
correspond  to  the  NO  previously  present.  There  must  be  an 
excess  of  oxygen  remaining  at  the  end  of  the  process.  The 
sticks  of  caustic  potash  must  be  perfectly  dry  (Klinger,  Ber., 
1913,  p.  1746).  The  formation  of  NO2  in  lieu  of  N2O3  is  not 
caused  by  an  excess  of  oxygen,  but  by  the  presence  of 
moisture. 

If  the  NO  is  in  excess,  all  the  oxygen  vanishes,  and  thus 
the  latter  can  be  estimated  (supra,  p.  217). 

Koehler  and  Marqueyrol  (Bull.  Soc.  Chini.,  xiii.  p.  69; 
/.  Chem.  Soc.,  civ.  p.  241  ;  Chem.  Zentralb.,  1913,  p.  957) 
prefer  absorbing  the  N2O3  formed  as  above,  not  by  potassium 
hydroxide,  but  by  monoethylaniline,  because  the  potassium 
hydroxide  absorbs  also  several  other  gases  (N2O,  N2,  CO2,  CO). 
Monoethylaniline  dissolves  a  little  more  than  its  own  volume 
at  CO2  at  15°  to  20°  under  atmospheric  pressure,  so  that  when 
only  one-sixth  or  one-seventh  of  the  total  pressure  is  due  to  this 
gas,  the  volume  dissolved  by  the  small  amount  of  ethylaniline 
used  can  be  neglected.  They  introduce  80  c.c.  of  the  gas  into  a 
glass  jar,  standing  in  a  mercury  trough,  together  with  0-6  c.c. 
monoethylaniline,  and  by  a  Doyere  pipette  they  admit  oxygen 


NITRIC  OXIDE  319 

bubble  by  bubble,  so  that  after  the  absorption  of  all  the  NO 
about  5  c.c.  remain  behind  The  gas  is  then  separated  from 
the  liquid,  measured,  and  the  CO2  absorbed  by  0-2  c.c.  standard 
alkali  solution,  after  which  the  gas  is  again  measured. 

To  test  whether  all  the  nitric  oxide  has  been  absorbed  by 
one  of  oxidising  agents  employed,  Lunge  and  Ilosvay  (Z. 
angew.  Chem.,  1890,  p.  568)  employ  the  reagent  of  Griess  as 
modified  by  Lunge  (vide  supra,  p.  316)  by  allowing  the  air  to 
mix  with  the  gases  as  they  leave  the  bulb-tube,  and  then 
examining  for  higher  oxides  of  nitrogen.  The  above  reagent 
will  always  show  a  slight  reddening  with  such  gases,  even  where 
the  absorption  has  been  made  as  complete  as  possible  ;  but  for 
most  practical  purposes  such  traces  may  be  neglected. 

IV.  Reaction  of  Nitric  Oxide  with  Hydrogen.  —  Knorre  and 
Arendt  (Ber.,  1899,  p.  2136)  mix  the  gas  with  hydrogen  and  pass 
the  mixture  very  slowly  through  a  Drehschmidt's  platinum 
capillary  (p.  100),  heated  to  a  bright  red  heat.  Under  these 
circumstances  the  combustion  takes  place  according  to  the 
following  equation  : 


2  =  2H2O  +  N2. 

4  vols.      4  vols.  0  vol.      2  vols. 

Hence  each  volume  of  nitric  oxide  present  corresponds  to  aeon- 
traction  of  ij  volumes,  or  two-thirds  of  the  contraction  =  NO. 
If  the  gas  is  passed  too  quickly  or  the  heating  of  the  capillary 
is  insufficient,  some  ammonia  is  formed,  producing  wrong 
results. 

Nitric  oxide  cannot  be  burned  by  explosion  with  hydrogen  ; 
if,  however,  much  nitrogen  protoxide  is  present,  there  is  a 
violent  explosion,  but  no  quantitative  combustion  of  the 
nitric  oxide. 

V.  Reaction  of  Nitric  Oxide  with  Carbon  Monoxide.  —  L. 
Pollak  (as  quoted  by  Treadwell,  vol.  ii.  p.  567)  found  that  a 
mixture  of  NO  and  CO  can  be  burnt  by  passing  it  through 
a  Drehschmidt's  platinum  capillary,  if  at  the  same  time  the 
carbon  dioxide  formed  is  removed.  This  is  done  by  placing 
on  the  mercury  in  the  pipette  connected  with  the  Drehschmidt 
capillary  a  few  cubic  centimetres  of  caustic  potash  solution, 
which  absorbs  the  CO2  as  it  is  formed.  If  this  is  neglected, 
the  combustion  is  not  quantitative. 


320  TECHNICAL  GAS-ANALYSIS 

The  reaction  is  : 


2NO  +  2CO  = 

4  vols.      4  vols.  0  vol.       2  vols. 

corresponding  to  a  contraction  =  —  of  the  volume  of  NO. 

If  at  the  same  time  much  nitrogen  protoxide  is  present, 
the  combustion  of  the  NO  in  the  Drehschmidt  capillary  is 
quantitative,  even  without  absorbing  the  CO2  formed  : 

2NO  +  2CO  -  CO2  +  N2. 

4  vols.      4  vols.         4  vols.    2  vols. 

Here  the  contraction  is  =  —  vol.  of  the  nitric  oxide. 

2 

Analysis  of  Gas  Mixtures  containing  both  Nitrogen  Protoxide 
and  Nitric  Oxide  (Moser,  Z.  anal.  Chem.,  1911,  1.  p.  401).  —  The 
separation  of  N2O  and  NO  cannot  be  effected  by  dissolving 
out  the  NO  by  means  of  a  solution  of  ferrous  sulphate, 
for  the  N2O  is  soluble  to  some  extent  in  water,  even  when 
this  is  saturated  with  a  salt  such  as  ferrous  sulphate.  Previous 
saturation  of  the  ferrous  sulphate  solution  with  nitrous  oxide 
changes  the  large  positive  error  to  a  small,  but  not  insignificant 
negative  one,  for  the  absorption  of  NO  by  the  liquid  reduces 
its  capacity  to  hold  N2O  in  solution,  and  this  gas  is  set  free. 
The  method  proposed  by  Divers  (Trans.  Chem.  Soc.,  1889, 
p.  82  ;  vide  supra  ^.  317)  viz.,  absorption  of  the  NO  by  sodium 
sulphite  solution,  gives  no  better  results.  The  gravimetric 
methods  for  the  estimation  of  NO  are  very  troublesome  and 
rarely  applicable.  The  volumetric  method  of  oxidising  the 
NO  by  permanganate,  which  has  no  action  on  N2O,  for  which 
Lunge  (Z.  angew.  Chein.,  1890,  p.  568)  has  designed  a  special 
apparatus  (the  ten-bulb  tube,  p.  146),  may  also  lead  indirectly 
to  errors,  owing  to  the  necessity  of  displacing  the  air  by  CO2. 
This  is  avoided  by  Moser,  by  passing  the  gas  to  be  analysed 
into  an  absorption  vessel  previously  filled  with  standardised 
potassium  permanganate  solution  ;  after  shaking  well  to 
complete  the  reaction,  the  diminution  in  the  strength  of  the 
permanganate  is  measured.  Or  else  the  apparatus  is  filled 
with  hydrogen  peroxide  solution,  and  the  nitric  acid  formed 
from  the  NO  determined  by  titration  with  standard  alkali. 
Of  course  here  the  presence  of  acid  vapours  must  be  avoided. 


NITROGEN  PROTOXIDE,  ETC.  321 

The  following  method  for  estimating  both  NO  and  N0O 
has  been  proposed  by  Knorre  (loc.  cit.)  : — The  gas  is  mixed  with 
an  excess  of  hydrogen  and  burnt  in  a  bright  red-hot  Drehschmidt 
capillary.  If  we  call  the  volume  of  N2O=;tr,  that  of  NO=j, 
we  have : 

N2O      NO 

x    +    y      =  V 

x  +  3-y  =  Vc  (contraction), 

from  which  we  find  : 

x  =•  3V-2VC 
y   =  2(VC-V). 

Or  else  the  gaseous  mixture  is  mixed  with  an  excess  of 
carbon  monoxide^  burnt  in  the  bright  red-hot  Drehschmidt 
capillary,  and  the  contraction  (Vc)  and  the  CO2  formed  (Vfc) 
are  measured : 

N20      NO 

x+y  =  Vk 


therefore : 


x  =  V,-2VC 
y   =  2VC. 


Moser  (loc.  cit.)  objects  to  the  estimation  of  N2O  by  burning 
a  mixture  of  it  with  hydrogen  that  ammonia  is  formed  as  a 
by-product,  and  that  platinum  is  permeable  to  gases  at  a 
red  heat. 

The  method  of  Baudisch  and  Klinger  (p.  318),  viz.,  oxidation 
of  the  NO  to  N2O3,  may  also  be  used  in  the  presence  of  N2O. 

Estimation  of  Nitrogen  Protoxide,  Nitric  Oxide^  and  Free 
Nitrogen  in  Presence  of  One  Another. — According  to  Knorre, 
either  by  burning  with  hydrogen  or  with  carbon  monoxide  in  the 
Drehschmidt  capillary.  In  the  case  of  hydrogen,  we  note  the 
contraction  (Vc),  add  to  the  gaseous  remainder  an  excess  of 
oxygen,  and  burn  in  the  capillary.  Two-thirds  of  the  ensuing 
contraction  is  equal  to  the  hydrogen  not  consumed  in  the  first 

x 


322  TECHNICAL  GAS-ANALYSIS 

combustion;  this    magnitude,    deducted    from    the    hydrogen 
originally  used,  indicates  the  hydrogen  consumed  (Vw). 
Now  we  have  : 

N2O     NO       N 

x  +  y    +  z  =  V 

x  +  ?-y         =  V 

x  +  y  =  Vw 

from  which  we  find  : 

x  =  3VW-2VC 
y  =  2(VC-VJ 
z  =  V-VW. 

If  we  burn  the  gases  with  carbon  monoxide,  we  have  : 
N2O     NO     N 

X    +     y       +    Z    =    V 

—  y  =  Vc  (contraction). 

-*   +   y  =  V*  (carbon  dioxide), 

from  which  we  find  : 

*  =  V,-2VC 

y  =  2VC 


In  gaseous  mixtures  containing,  besides  N2O,  NO,  and  N, 
also  carbon  dioxide,  this  must  be  first  absorbed  by  the  smallest 
possible  quantity  of  highly  concentrated  caustic  potash  solution, 
whereupon  the  analysis  of  the  gaseous  remainder  is  performed 
as  just  described. 

Nitrogen   Trioxide  and  Peroxide. 

Reich's  method  (supra,  p.  1  37)  has  been  also  applied  to  the 
estimation  of  the  active  nitrogen  acid  equivalent  to  nitrogen 
trioxide,  N2O3,  in  the  gases  of  vitriol-chambers  and  Gay- 
Lussac  towers,  etc.  The  absorbent  is  a  decinormal  solution  of 
potassium  permanganate,  mixed  with  about  the  same  volume 
of  dilute  sulphuric  acid.  The  end  of  the  reaction  is  indicated 
by  the  liquid  being  decolorised,  but  the  absorption  takes  place 
slowly  and  somewhat  incompletely.  We  must,  moreover, 


NITROUS  FUMES  323 

consider  that  the  atmosphere  of  the  vitriol-chambers  does  not 
contain  the  active  nitrogen  oxides  in  the  shape  of  N2O3,  as 
formerly  assumed,  but  that  the  nitrogen  trioxide  is  almost 
entirely  dissociated  into  nitric  oxide  and  nitric  peroxide, 
mostly  together  with  an  excess  of  either  one  or  the  other  of 
these  oxides.  By  the  method  just  described  we  learn  how 
much  of  the  exact  mixture  of  NO  +  NO2  ^!  N2O3  is  present. 
But  as  in  most  cases  the  chamber-gases  contain  an  excess  of 
either  NO  or  NO2  above  that  proportion,  the  operation  of 
determining  by  Reich's  or  any  other  method  the  amount  of 
oxygen  required  for  forming  nitric  acid  is  quite  inaccurate. 
This  also  holds  good  of  the  modification,  consisting  in  passing 
a  certain  volume  of  the  chamber-gases  through  concentrated 
sulphuric  acid,  which  certainly  retains  the  mixture  of  NO-f-NO2 
in  the  shape  of  nitrososulphuric  acid,  but  also  any  NO2 
present  in  excess,  in  the  shape  of  nitrososulphuric  acid  and 
nitric  acid;  the  latter  would  not  be  indicated  when  titrating 
the  solution  with  potassium  permanganate.  If,  on  the  contrary, 
NO  is  in  excess,  this  would  be  lost.  That  solution  of  nitrogen 
oxides  in  concentrated  sulphuric  acid  should  not  be  tested  by 
the  permanganate  method  (by  which  any  NO3H  formed  from 
NO2  would  be  lost),  but  by  the  nitrometer  to  be  described. 
In  the  back  chambers  there  is  an  excess  of  NO2  in  the  gases,  and 
here  the  mixture  of  nitrogen  oxides  can  be  directly  absorbed  in 
concentrated  sulphuric  acid,  and  then  tested  in  the  nitrometer. 
In  the  front  chamber  there  is  an  excess  of  NO,  and  here  the 
gases,  after  absorption  by  concentrated  sulphuric  acid,  should 
be  oxidised  by  permanganate  as  described  supra>  p.  317,  and 
the  solution  obtained  again  tested  in  the  nitrometer. 

Estimation  of  Nitrous  Fumes  produced  by  Explosion. — Hey- 
mann  (/.  Soc.  Chem.  Ind.y  1913,  xxxii.  p.  674)  estimates  the 
nitrous  fumes,  produced  especially  by  the  explosion  of  "cheesa  " 
sticks,  by  means  of  a  bottle  containing  at  the  bottom  a  solution 
of  sodium  hydroxide,  through  the  cork  of  which  pass  three 
copper  wires,  one  of  them  for  carrying  a  small  porcelain 
crucible  containing  the  substance  to  be  treated ;  the  other 
two  wires,  dipping  into  the  crucible,  are  connected  by  a  thin 
platinum  wire,  and  outside  the  bottle  with  a  storage  battery,  so 
that  the  substance  can  be  ignited  by  turning  on  the  current. 
The  fumes  evolved  are  absorbed  by  the  caustic  soda  solution, 


324  TECHNICAL  GAS-ANALYSIS 

and  ultimately  the  nitrogen  oxides  contained  therein  are 
reduced  by  zinc,  the  ammonia  evolved  indicating  the  amount 
of  nitrogen  oxides. 

Free  Nitrogen. 

Nitrogen  can  be  completely  oxidised  to  nitric  acid  by 
mixing  it  with  oxygen  and  treating  the  mixture  with  strong 
electric  sparks.  According  to  Hempel  (Gasanal.  Methoden^ 
4th  ed.,  p.  148),  it  is  absorbed  by  a  red-hot  mixture  of  I  g. 
magnesium,  5  g.  freshly  ignited  lime,  and  0-25  g.  sodium.  But 
these  methods  are  only  used  for  isolating  the  helium,  etc., 
accompanying  it  in  atmospheric  air,  in  gases  from  mineral 
springs,  etc.,  which  are  not  oxidised  or  absorbed  by  these 
methods. 

In  the  ordinary  way  of  technical  gas-analysis,  the  nitrogen 
is  only  estimated  by  difference,  after  estimating  all  other 
gaseous  constituents  present. 

Nitrogen,  according  to  Bunsen,  is  not  burnt  when  exploding 
fulminating  gas  in  presence  of  air,  if  no  more  than  30  vols.  of 
combustible  gas  is  present  to  100  vols.  of  incombustible  gas. 
When  burning  gases  containing  nitrogen  by  the  Drehschmidt 
platinum  capillary,  no  nitrogen  is  oxidised. 

Ferry's  apparatus  for  the  volumetric  estimation  of  nitrogen 
(sold  by  Greiner  and  Friedrichs,  Stiitzerbach,  Chem.  Zeit.  Rep., 
1912,  p.  349)  contains  a  cylinder  where  CO2  is  retained  by 
caustic  potash  solution,  with  a  spiral  for  the  better  contact  of 
the  gas  with  the  solution  ;  on  the  top  of  the  cylinder  there  is  a 
glass  tap,  surmounted  by  a  dish  where  the  nitrogen,  now  free 
from  CO2,  is  carried  into  a  measuring-tube,  employing  another 
confining  liquid. 

The  apparatus  of  Henrich  and  Eichhorn  for  removing  free 
nitrogen  from  gaseous  mixtures  by  burning  with  oxygen 
through  the  action  of  electric  sparks  has  been  mentic  led 
supra,  p.  172. 

Natus  (Z.  anal.  Chem.,  1913,  pp.  265  et  seq.}  effects  the 
direct  determination  of  elementary  nitrogen  in  gaseous 
mixtures  with  the  help  of  calcium  carbide  (already  recom- 
mended by  Franz  Fischer  and  Ringe  in  Ber.,  1908,  p.  2017). 
He  absorbs  it  by  contact  with  a  finely  powdered  mixture 


AMMONIA  325 

of  commercial  calcium  carbide  with  one-tenth  of  its  weight  of 
fused  calcium  chloride  at  900°  to  1000°.  The  product  (calcium 
cyanamide)  is  then  treated  by  Wilfarth's  modification  of  Kjel- 
dahl's  method  (in  which  the  substance  is  heated  with  a  mixture 
of  concentrated  and  fuming  sulphuric  acids  and  a  drop  of 
mercury).  A  known  weight  of  the  carbide  mixture  (previously 
heated  in  a  current  of  hydrogen  to  remove  volatile  impurities) 
is  introduced  into  a  porcelain  boat  within  a  porcelain  tube 
which  is  connected  at  either  end  with  gas-burettes;  the 
apparatus  is  filled  with  pure,  dry  hydrogen,  and  then  the 
carbide  is  heated,  and  the  gas  to  be  absorbed  is  introduced, 
the  absorption  being  completed  by  slowly  passing  the  gaseous 
residue  twice  backwards  and  forwards  through  the  tube.  The 
absorption  product,  after  cooling,  is  transferred  to  the  decom- 
position flask  and  at  once  moistened  with  sulphuric  acid  (not 
water);  decomposition  is  complete  in  about  an  hour  with 
Wilfarth's  mixture,  and  the  cool  diluted  liquid  is  rendered 
alkaline,  treated  quickly  with  potassium  sulphate  solution,  and 
distilled  in  the  presence  of  zinc  dust.  The  average  loss  of 
nitrogen  in  the  process  (with  water  in  the  gas-burettes)  is 
1-9  per  cent,  (maximum  3-6),  or,  with  dry  gas  contained  over 
mercury,  0-75  per  cent,  (maximum  1-4). 

Ammonia. 

The  estimation  of  ammonia  in  technical  gas-analysis  takes 
place  in  the  manufacture  of  illuminating  gas,  from  which  it 
must  be  completely  removed,  both  for  its  use  for  lighting  and 
for  heating  purposes,  apart  from  its  utilisation  as  a  valuable 
by-product  of  the  gas  manufacture. 

Its  estimation  in  the  crude  gas  has  the  object  of  ascertaining 
the  yield  of  NH3  from  the  coal  carbonised,  but  more  particularly 
of  checking  the  work  of  the  scrubbers  or  other  apparatus 
applied  for  removing  it  from  the  gas.  Thus,  for  instance,  the 
gas  from  the  retorts  may  per  100  cb.m.  contain  412  g.,  in 
front  of  the  scrubbers  375  g.,  behind  the  scrubbers  0-9  g., 
behind  the  oxide  of  iron  purifiers  merely  a  trace  of  NH3. 

In  normal  working  like  this,  the  removal  of  the  ammonia 
from  the  gas  is  practically  complete,  but  in  case  of  disturbances, 
£.£•.,  when  overtasking  the  apparatus  by  a  sudden  increase  of 


326  TECHNICAL  GAS-ANALYSIS 

the  production  of  gas,  or  by  insufficient  cooling,  or  mistakes 
made  in  the  working  of  the  scrubbers,  etc.,  on  the  other  hand, 
10  or  up  to  20  per  cent,  of  the  ammonia  may  remain  in 
the  gas. 

In  properly  purified  street-gas  there  are  only  slight  traces  of 
ammonia,  hardly  ever  more  than  0-5  g.  per  100  cb.m.  In 
England  0-5  to  2-0  grains  NH3  per  100  cb.  ft.  is  the  maximum 
allowed. 

Still,  an  occasional  control  of  this  should  be  made,  for  even 
such  slight  quantities  of  ammonia  may  do  damage,  e.g.,  by  the 
formation  of  cyanogen  hydride  in  gas  burning  with  a  smoky 
flame,  by  the  formation  of  traces  of  nitric  oxide  and  nitrogen 
trioxide,  by  acting  on  the  metal  of  the  gas-meters,  etc. 

The  estimation  of  ammonia,  both  in  the  crude  and  in  the 
purified  gas,  takes  place  by  absorption  and  titration  with 
standard  acid  ;  normal  or  seminormal  acid  being  used  for  crude 
gas,  decinormal  acid  for  street-gas.  The  best  indicator  is  an 
aqueous  solution  of  methyl  orange  (i  :  1000  water),  or  an 
alcoholic  solution  of  dimethyl  -  amidoazobenzene  (i  :  200). 
When  testing  crude  gas  containing  much  tar,  which  imparts  a 
brown  colour  to  the  absorbing  liquid,  fluorescein  is  preferable ; 
it  indicates  the  neutralisation  of  the  acid  by  the  cessation  of  the 
fluorescence,  which  is  best  observed  when  placing  the  glass  on 
glazed  black  paper.  Both  these  indicators  are  not  affected  by 
carbon  dioxide  or  hydrogen  sulphide,  whilst  rosolic  acid  is  not 
quite  unaffected  by  them. 

The  absorption  of  the  ammonia  by  the  standard  acid  is 
carried  out  in  one  of  the  numerous  apparatus  constructed  for 
such  purposes,  many  of  which  have  been  described  in  previous 
chapters,  *.£-.,  pp.  65,  71,  76,  84,  102,  106,  145,  146,  147.  Care 
must  be  taken  that  the  glass  of  which  they  are  made  has  not 
by  itself  an  alkaline  reaction,  and  that  a  minimum  of  rubber 
tubing  is  used  for  making  the  connections.  In  the  case  of 
uiiscrubbed  gas  the  sample  should  always  be  taken  by  means 
of  a  tube  projecting  into  the  main,  as  the  inner  surface  of 
the  latter  is  always  coated  with  tar.  Even  when  using  all 
precautions,  exact  results  are  sometimes  difficult  to  obtain 
on  account  of  the  tar-fog  present  in  crude  gas,  which  makes 
the  end-point  of  the  titration  more  difficult  to  observe.  If 
this  tar-fog  is  removed  by  a  cotton-wool  filter,  as  described 


AMMONIA  327 

on  pp.  307  et  seq.)  the  results  are  too  low,  because  the  filters  also 
remove  some  of  the  ammonia  from  the  gases.  On  the  whole, 
it  is  best  not  to  attempt  removing  the  tar-fog,  and  to  allow  for 
the  fact  that  the  tendency  is  then  for  the  results  to  be  rather 
too  high.  In  case  of  necessity  the  ammonia  may  be  estimated 
in  the  ammonium  sulphate  obtained  by  Knop's  well-known 
azotometer. 

When  testing  crude  gas  containing  very  much  ammonia, 
the  quantity  of  gas  required  for  a  test  is  correspondingly  small, 
and  this  is  often  conveniently  measured  by  a  graduated 
aspirator  instead  of  a  meter.  This  is  even  necessary  where  the 
gas  to  be  tested  is  under  a  pressure  less  than  that  of  the 
atmosphere,  in  which  case  the  aspirator  draws  the  gas  from  the 
main  through  the  absorbing  apparatus.  Where  a  meter  is 
used,  and  the  gas  contains  sulphuretted  hydrogen,  a  small 
oxide  of  iron  purifier  should  be  placed  between  the  absorbing 
apparatus  and  the  meter,  as  otherwise  the  metal  of  the  latter 
would  be  rapidly  corroded. 

The  determination  of  ammonia  in  illuminating  gas  is  treated 

in  a  technologic  paper  No.  34,  of  the  U.S.  Bureau  of  Standards. 

For  testing  street-gas,  S.  Elster,  of  Berlin,  sells  a  gas-meter 

which  after  the  passage  of  100  litres  automatically  interrupts 

the  further  passage. 

In  Pfeiffer's  method  for  estimating  the  naphthalene  vapour 
in  gas,  described  suprd,  p.  300,  the  ammonia  contained  in  the 
gas  must  be  completely  retained  by  an  acid  washing,  and  this 
may  be  used  for  estimating  its  quantity  at  the  same  time. 

L.  W.  Winkler  (Z.  angew.  Chem.,  1913,  p.  231)  absorbs  the 
ammonia  by  a  solution  of  boric  acid  and  titrates  it  by  standard 
acid,  employing  congo-red  or  methyl  orange  as  indicator. 

The  estimation  of  pyridine  in  the  presence  of  ammonia  is 
effected  by  Bayer  (/.  Gasbeleucht.,  1912,  p.  513)  by  precipitating 
the  ammonia  in  the  shape  of  ammonia-magnesia  phosphate, 
filtering,  distilling  the  filtrate  and  titrating  the  distillate, 
ferrirhodanide  serving  as  indicator. 

Baessler  (/.  Gasbeleucht.,  1912,  p.  905)  distils  solutions 
containing  both  ammonia  and  pyridine,  with  an  excess  of 
caustic  soda,  decomposes  the  ammonia  contained  in  the 
distillate  by  sodium  hypobromite  solution,  and  distils  the 
pyridine  remaining  behind  into  standard  sulphuric  acid. 


328  TECHNICAL  GAS-ANALYSIS 

Cyanogen  and  Hydrogen  Cyanide. 

About  2  or  3  per  cent,  of  the  nitrogen  of  the  coal  is  in  its 
dry  distillation  converted  into  cyanogen  and  its  compounds.  A 
small  portion  of  this  is  retained  in  the  hydraulic  main,  the  coolers 
and  scrubbers,  much  more  of  it  in  the  oxide  of  iron  purifiers, 
but  some  of  the  cyanogen  always  remains  in  the  street-gas. 
The  cyanogen  compounds  retained  in  the  purifiers  impart  a 
much  greater  value  to  the  spent  oxide  than  it  would  otherwise 
possess,  wherefore  their  estimation  in  the  crude  gas  and  the 
purified  gas  is  of  economical  importance.  Drehschmidt 
(/.  Gasbeleucht.,  1892,  p.  268)  calculated  that  already  at  that 
time  the  cyanogen  remaining  in  the  street-gas  of  Berlin  repre- 
sented a  value  of  £2150  per  annum. 

In  a  special  instance,  Leybold  (/.  Gasbeleucht^  1890,  p.  366) 
found  in  100  cb.m.  gas  the  following  quantities  of  cyanogen  or 
its  compounds : — 

In  the  hydraulic  main     ....       256-1  g. 
After  cooling        .....       246-5  „ 
„      scrubbing  .....       242-4  „ 
„     the  first  oxide  purifier     .  .  .       126-8  „ 

„     the  second          „  ...        80-2  „ 

„     the  third  „  ...         59-3  „ 

In  the  gas-holder  ....        39-7  „ 

Removed  by  cooling        .         •  ^    .        .  3.76  per  cent. 

„  scrubbing  .  .  ^  .         1-62         „ 

„  oxide  (i)     .  .  ..         45-09        „        \ 

„  „     (2)     .  .  .         18-12        „         ^71-45  per  cent. 

„  „      (3)     -  •  •.  8-16        „        J 

Remaining  in  the  street-gas       .  .         15-50        „ 

The  hydrogen  cyanide  present  in  street-gas  must  strongly 
increase  its  poisonous  properties,  whilst  free  cyanogen  (di- 
cyanogen)  is  not  poisonous.  Unfortunately  no  analytical 
methods  exist  for  the  quantitative  separation  of  HCN  and 
NC  =  CN.  Both  of  them,  however,  quickly  destroy  the  iron 
parts  of  the  gasholders  and  the  metal  of  the  meters,  unless  these 
are  specially  protected. 

The  qualitative  detection  of  cyanogen,  either  free  or  in  the 
state  of  HCN,  is  effected  according  to  Kunz-Krause  (Z.  angew. 
Chem.y  1901,  p.  652),  who  bases  himself  on  a  reaction  indicated 
by  Schonbein  and  Pagenstecher,  by  filtering  paper,  soaked 


CYANOGEN  AND  HYDROGEN  CYANIDE 


329 


successively  in  a  solution  of  cupric  sulphate  (i  :  1000)  and 
freshly  prepared  tincture  of  guaiac  resin  (3  per  cent.),  which  is 
thereby  coloured  blue.  This  extremely  sensitive  reaction  can 
do  very  good  service  in  the  detection  of  very  slight  escapes  of 
coal-gas.  Schaer  has  made  it  even  more  sensitive  by  using 
guaiaconic  acid  in  place  of  the  gum  guaiac.  Brunnich  (Chem. 
News,  cxxxvii.  p.  173)  moistens  the  test  paper  with  formalin 
before  exposing  it  to  the  gas  mixture. 

The  quantitative  estimation  of  the  total  cyanogen  contained 
in  the  crude  or  purified  gas  is  mostly  effected  by  a  process  first 
indicated  by  Gasch  (/.  Gasbeleucht.,  1890,  p.  215)  which  we 
describe  in  the  form  given  to  it  by  Drehschmidt  (loc.  cit.).  Both 
free  cyanogen  and  hydrocyanic  acid  are  re- 
tained, even  in  the  presence  of  CO2  and  H2S,  by 
a  solution  of  potassium  hydroxide,  containing 
freshly  precipitated  ferrous  hydrate,  with  forma- 
tion of  ferrocyanide.  For  each  test  100  litres 
of  gas,  at  the  rate  of  60  litres  per  hour,  is 
passed  through  two  bottles  of  the  shape  shown 
in  Fig.  124,  where  the  entrance  pipe  ends  at 
the  bottom  of  the  bottle  in  a  perforated  bulb. 
The  first  bottle  is  charged  with  15  c.c.  of  a 
solution  of  ferrous  sulphate  (i  :  10)  and  15  c.c. 
of  a  solution  of  commercial  caustic  potash 
(1:3);  the  second  with  5  c.c.  of  ferrous  sulphate 
solution,  5  c.c.  caustic  potash  solution,  and  20 
c.c.  water.  Behind  these  comes  the  gas-meter, 
of  the  test  the  contents  of  both  bottles  are  washed  out, 
made  up  to  250  c.c.,  and  poured  on  to  a  dry  filter.  Two 
hundred  c.c.  of  the  clear  filtrate  =  80  litres  gas  is  neutralised 
with  sulphuric  acid;  add  2  g.  ammonium  sulphate,  15  g. 
mercuric  oxide  (to  remove  H2S),  and  a  few  drops  of  liquor 
ammonias,  heat  to  boiling,  and  continue  this  gently  for  a  quarter  of 
an  hour.  After  cooling  dilute  to  300  c.c.  and  filter  again  through 
a  dry  filter.  Of  the  clear  liquor  thus  obtained,  pour  250  c.c., 
corresponding  to  66-66  litres  of  gas,  into  a  300  c.c.  flask,  add  6 
or  8  c.c.  of  liquor  ammoniae  sp.  gr.  0-91,  and  7  g.  zinc  dust,  shake 
well  up,  add  2  c.c.  caustic-potash  solution  (i  13),  fill  up  to  the 
mark,  shake  up  again,  and  filter  through  a  double  filter.  Titrate 
200  c.c.  of  the  fitrate  =  44-44  litres  gas,  by  adding  10  c.c.  deci- 


FIG.  124. 
At  the  end 


330  TECHNICAL  GAS-ANALYSIS 

normal  silver  solution,  acidulating  with  nitric  acid,  and 
remeasuring  the  excess  of  silver  by  decinormal  ammonium 
sulphocyanide  solution  and  iron  alum  as  indicator.  Each  cubic 
centimetre  TV  normal  silver  nitrate  consumed  =  0-002584  g. 
cyanogen. 

The  ferrocyanide  contained   in  the  absorbing  bottles  can 
also  be  estimated  by  the  method  of  Feld  (/.  Gasbeleucht.,  1903, 
p.  561),  which  is  founded  upon  a  method  proposed  by  Rose  and 
Finkener  (Z.  anal.  Chem.,  1862,  p.  299).     It  is  founded  on  the 
fact  that  mercuric  oxide  converts  a  boiling  solution  of  a  soluble 
ferrocyanide  into  mercuric  cyanide,  from  which  the  hydrocyanic 
acid  may  then  be  recovered  by  distillation  with  sulphuric  acid 
in  presence  of  chlorides.     A  solution  containing  about  0-3  to 
°'5  g-  °f  potassium  ferrocyanide  or  its  equivalent,  freed  from 
sulphide  by  lead  carbonate,  if  necessary,  is  diluted  to  about  150 
c.c.,  10  c.c.  of  normal  sodium  hydroxide  solution  added,  and 
the   mixture   heated   to   boiling.      Then    15   c.c.  of  trinormal 
magnesium  chloride  solution  is  added  in  a  thin  stream,  and  the 
boiling  continued  for  five  minutes.     One  hundred  c.c.  of  boiling 
decinormal  mercuric  chloride  solution  are  then  added,  and  the 
boiling  continued  for  a  further  ten  minutes,  after  which  the 
flask  is  connected  to  a  condenser,  30  c.c.  of  4  N-sulphuric  acid 
run  in  by  means  of  a  stoppered  funnel,  and  the  distillation  is 
continued  for  twenty  to  thirty  minutes,  the  end  of  the  condenser 
dipping  under  the  surface  of  25  c.c.  of  normal  sodium  hydroxide 
solution,  placed  in  the  receiver.     Thereby  the  HCN  present  as 
ferrocyanide  is  obtained  in  the  receiver  as  a  solution  of  sodium 
cyanide,  the  amount  of  which  is  determined  by  dilution  to  300 
to  400  c.c.,  adding  a  little  potassium  iodide  and  titrating  with 
decinormal  silver  nitrate  until  a  permanent  yellow  precipitate 
of  Agl    is   formed.      Each   cubic   centimetre   of  'N\\Q  silver 
nitrate  solution  indicates  0-0052  g.  NC=CN,  0-005403  g.  HCN, 
0-01409  g.  K4  Fe  (CN)6.  3H2O,  or  0-00956  of  Fe7  (CN)18. 

Many  analysts  have  approved  of  this  method.  Skirrow 
(/.  Soc.  Chem.  Ind.,  1910,  p.  319)  obtained  with  it  low  results, 
but  Colmann  (Analyst,  1910,  p.  295)  states  the  results  to  be 
substantially  accurate.  Pfeiffer  (Lunge-Berl's  Unt.  Meth.,  iii. 
p.  343)  approves  of  it  as  well. 

Detection  and  Determination  of  Cyanogen  in  Presence  of 
Hydrogen  Cyanide. — Rhodes  (J.  Ind.  and  Eng.  Chem.,  1912,  iv. 


CYANOGEN  AND  HYDROGEN  CYANIDE  331 

p.  652),  basing  upon  an  observation  made  by  Wallis  (Liebig's 
Ann.,  1906,  cccxlv.  p.  353),  proceeds  as  follows: — Test-tubes 
15  c.m.  long  and  provided  with  side  arms  are  used  for  absorbing 
the  gases.  In  one  such  tube  is  placed  10  c.c.  of  a  10  per  cent, 
solution  of  silver  nitrate  to  which  I  drop  of  J  normal  nitric 
has  been  added.  In  the  second  tube  is  placed  10  c.c.  of  a 
twice-normal  solution  of  potassium  hydroxide.  The  two 
absorption  tubes  are  connected  in  series  and  the  gas  mixture 
is  passed  through.  Since  the  first  tube  is  intended  to  hold 
back  the  hydrogen  cyanide,  the  passage  of  the  gas  must  be 
stopped  before  all  the  silver  nitrate  in  this  tube  has  been 
converted  into  cyanide.  After  the  gas  mixture  has  been 
passed  through  for  a  sufficient  length  of  time,  a  current  of  air 
is  passed  through  for  ten  minutes.  The  second  tube,  which 
contains  the  potassium  hydrate  solution,  is  then  disconnected, 
and  5  c.c.  of  a  solution  of  ferrous  sulphate  and  I  drop  of 
a  solution  of  ferric  chloride  are  added  to  its  contents;  after 
about  fifteen  minutes  dilute  sulphuric  acid  is  added,  to  dissolve 
the  ferrous  and  ferric  hydroxide.  The  appearance  of  a  blue- 
green  colour  after  acidification  proves  the  presence  of  cyanogen 
in  the  original  gas  mixture.  As  small  an  amount  of  cyanogen 
as  0-3  c.c.  may  be  detected  in  this  manner,  even  in  the  presence 
of  10  c.c.  of  hydrogen  cyanide,  and  even  when  20  litres  of 
air  was  passed  through  the  apparatus  subsequent  to  the 
introduction  of  the  cyanogen.  Carbon  dioxide  interferes 
only  if  sufficient  of  it  is  present  to  convert  all  the  KOH  into 
K2CO3.  The  presence  of  hydrogen  cyanide  in  the  original 
gas  mixture  is  detected  by  collecting  on  a  filter  any  precipitate 
formed  in  the  first  absorption  tube  which  contains  the  silver 
nitrate,  washing  it  with  very  dilute  nitric  acid,  drying  it, 
transferring  it  to  a  small  sublimation  tube,  and  warming  it 
with  about  5  mg.  of  iodine.  The  formation  of  a  sublimate  of 
cyanogen  iodide  on  the  side  of  the  tube  proves  the  presence 
of  silver  cyanide  in  the  precipitate;  o-i  mg.  of  silver  cyanide, 
equivalent  to  0-02  mg.  of  hydrogen  cyanide,  may  be  detected 
in  this  manner. 

To  determine  cyanogen  and  hydrogen  cyanide  in  the 
presence  of  each  other,  the  gas  mixture  is  passed  through  a 
series  of  four  absorption  tubes.  Each  of  the  first  two  of 
these  tubes  contains  5  c.c.  of  a  standardised  decinormal 


332  TECHNICAL  GAS-ANALYSIS 

solution  of  silver  nitrate  and  i  drop  of  dilute  nitric  acid ; 
the  third  tube  contains  10  c.c.  of  a  twice-normal  solution  of 
potassium  hydroxide,  free  from  chloride,  and  the  fourth  tube 
5  c.c.  of  this  solution.  The  gas  to  be  examined  is  slowly 
passed  through,  or  is  carried  through  by  a  slow  current  of 
air.  The  contents  of  the  first  two  absorption  tubes  are  placed 
on  a  filter,  and  the  soluble  silver  salts  washed  out  with  very 
dilute  nitric  acid.  The  filtrate  and  washings  are  titrated 
with  a  standardised  solution  of  ammonium  sulphocyanate, 
ammonium  ferric  alum  serving  as  indicator,  which  shows  the 
hydrogen  cyanide  present  in  the  original  gas  mixture.  The 
contents  of  the  third  and  fourth  absorption  tubes  are  placed 
in  a  beaker,  an  excess  of  a  standard  silver  nitrate  solution  is 
added,  constantly  stirring,  and  then  dilute  nitric  acid,  until 
the  silver  oxide  has  redissolved  and  the  solution  is  slightly 
acid.  The  precipitate  of  silver  cyanide  is  filtered  off,  the 
soluble  silver  salts  washed  out  with  very  dilute  acid,  and  the 
filtrate  and  washings  titrated  with  ammonium  sulphocyanide, 
ammonium-ferric  alum  serving  as  indicator.  From  this  the 
cyanogen  present  in  the  original  gas  mixture  is  calculated, 
the  reactions  being  : — 

(CN)2  +  2KOH     =  KCN  +  KCNO  +  H2O, 
KCN  +  AgNO3     =  AgCN  +  KNO3, 

AgN03  +  KCNS  =  AgCNS  +  KN03. 

Detection  of  Hydrogen  Cyanide. — We  have  spoken  of  this 
already  supra,  p.  328.  Another  test  for  it  is  the  formation  of 
Prussian  blue,  when  passing  the  gas  through  a  solution  of 
potassium  hydroxide,  adding  ferrous  sulphate  and  I  drop 
of  ferric  chloride,  gently  warming  and  acidifying  with  hydro- 
chloric acid.  Free  cyanogen  will  equally  produce  this  reaction. 

Or  else  add  ammonium  sulphide  in  excess,  then  ammonia 
or  a  drop  of  caustic  soda  solution,  and  heat  until  the  excess 
of  ammonium  sulphide  has  been  driven  off  and  the  solution 
is  again  colourless.  The  solution  will  then  contain  sulpho- 
cyanate, which  after  acidification  gives  a  blood-red  colour  with 
ferric  chloride. 

Quantitative  Determination  of  Hydrogen  Cyanide. — According 
to  L.  W.  Andrews  (Amer.  Chem.  /.,  1903,  xxx.  p.  187)  the  gas 
is  absorbed  in  potassium  hydroxide  solution,  which  is  diluted 


HYDROGEN  CHLORIDE  333 

until  it  contains  no  more  than  I  per  cent,  of  HCN.  Now 
2  drops  of  a  solution  of  paranitrophenol  are  added.  If 
thereby  a  yellow  colour  is  produced,  decinormal  hydrochloric 
acid  is  added  until  the  colour  has  nearly  disappeared.  On 
the  other  hand,  if  the  solution  remains  colourless,  decinormal 
caustic  potash  solution  is  added  until  a  very  pale  yellow  tint 
is  observed.  Now  add  15  to  20  c.c.  of  a  solution  of  40  g. 
of  mercuric  chloride  in  a  litre,  stir  the  solution  and  allow  it 
to  stand  for  one  hour  at  the  temperature  of  the  air.  The 
HC1  set  free  by  the  reaction  :  HgCl2+2HCN  =  Hg(CN)2+2HCl, 
is  then  titrated  with  a  decinormal  solution  of  potassium 
hydrate,  the  end-point  being  shown  by  the  appearance  of  a 
pale  yellow  tint  in  the  solution. 

Hydrogen  Chloride. 

This  gas  is  but  rarely  looked  for  in  technical  gases,  with 
two  certainly  most  important  exceptions,  viz.,  first,  the  exit- 
gases  from  the  ordinary  hydrochloric  acid  (muriatic  acid) 
condensers,  employed  in  the  saltcake  manufacture  by  the 
ordinary  process,  and  secondly,  in  the  gases  produced  in  the 
Hargreaves  process. 

I.  Exit-gases  from  the  Condensers  in  the  Manufacture  of 
Sulphate  of  Soda  from  Common  Salt  in  Decomposing  Pans. — 
According  to  the  British  Alkali  Act  of  1906,  95  per  cent,  of 
all  the  hydrochloric  acid  produced  in  a  works  must  be  con- 
densed, and  no  gases  are  permitted  to  escape  into  the  atmo- 
sphere which  contain  more  than  \  grain  HC1  per  cubic  foot 
(  =  0-457  g.  per  cubic  metre).  The  total  acidity  of  all  the 
gases  present  must  not  exceed  the  equivalent  of  4  grains 
SO3  per  cubic  foot  (  =  9-15  g.  per  cubic  metre).  The  volume 
of  the  gases  is  understood  as  reduced  to  60°  F.  (15-5°  C.)  and 
30  ins.  mercury  (almost  exactly  760  mm.). 

The  examination  of  the  chimney-gases  is  carried  out  by 
the  inspectors  by  means  of  a  Fletcher  bellows,  as  described  in 
Lunge's  Sulphuric  Acid  and  Alkali,  4th  ed.  1913,  i.  p.  768,  which 
serves  both  as  aspirator  and  absorbing  vessel ;  but  of  course 
any  other  of  the  various  absorbing  apparatus  described  in  this 
treatise  may  be  used  for  this  purpose.  The  Fletcher  bellows 
are  constructed  to  draw  TV  of  a  cubic  foot  of  gas  at  one 


334  TECHNICAL  GAS-ANALYSIS 

aspiration,  but  they  should  in  all  cases  be  standardised  by 
rilling  with  air  at  the  normal  working  capacity,  and  measuring 
the  volume  aspirated  by  expelling  it  into  an  inverted  graduated 
vessel  rilled  with  water,  correcting  the  volume  obtained  for 
temperature  and  pressure.  In  examining  chimney-gases  or 
other  gases,  the  bellows  are  connected  with  the  chimney  by 
means  of  a  porcelain,  glass,  or  platinum  tube  of  12  mm.  diameter, 
which  extends  some  considerable  distance  into  the  chimney. 
Both  bellows  and  tube  are  first  washed  out  with  distilled  water, 
200  to  300  c.c.  of  distilled  water  then  introduced,  and  the 
necessary  number  of  aspirations  made.  The  contents  of  the 
bellows  are  well  shaken  after  each  aspiration  to  allow  all  the 
acids  present  to  be  dissolved  by  the  water.  When  the  operation 
is  complete,  a  little  water  is  forced  into  the  connecting  tube 
and  allowed  to  flow  back  into  the  bellows  in  order  to  wash  out 
any  acid  that  may  have  condensed  in  the  tube.  The  liquid  in 
the  bellows  is  then  washed  into  a  porcelain  dish,  and,  if  necessary, 
filtered  from  soot.  Any  sulphurous  acid  present  is  oxidised  by 
potassium  permanganate,  excess  of  the  latter  removed  by  a 
trace  of  ferrous  sulphate,  the  solution  neutralised  by  pure 
sodium  carbonate,  a  little  potassium  chromate  added,  and  the 
whole  titrated  with  decinormal  or  centinormal  silver  nitrate 
solution.  Each  i  c.c  decinormal  silver  nitrate  solution 
=  0-003647  g.  HC1. 

In  the  Alkali  Inspectors'  Report  for  1898,  pp.  n  et  seq., 
an  addition  of  hydrogen  peroxide,  free  from  chlorine,  to  the 
water  put  into  the  bellows  was  recommended,  to  effect  the 
immediate  oxidation  of  any  sulphur  dioxide  present  in  the 
gases.  The  total  acidity  is  determined  by  titration  with  sodium 
carbonate  solution,  and  subsequently  the  chlorine  by  means 
of  standard  silver  nitrate  solution.  Certain  difficulties  are  liable 
to  occur  when  working  in  this  manner.  Thus  discoloration  may 
arise  owing  to  incomplete  oxidation  of  organic  matter  by  the 
hydrogen  peroxide,  and  this  may  under  certain  conditions  lead 
to  the  reduction  of  the  chromate ;  further,  it  is  difficult  to  obtain 
hydrogen  peroxide  free  from  chlorine.  For  these  reasons  the 
process  has  been  modified,  and  is  now  carried  out  as  follows  : — 
The  total  acidity  is  determined  as  before  with  sodium  carbonate 
solution  and  methyl  orange,  a  few  drops  of  potassium  per- 
manganate being  added  where  the  solution  is  very  dark  owing 


HARGREAVES  GASES  335 

to  the  presence  of  sooty  matter.  The  neutralised  solution  is 
treated  with  0-5  g.  of  calcium  or  magnesium  carbonate,  followed 
by  5  to  10  drops  of  a  5  per  cent,  ferrous  sulphate  solution,  the 
mixture  stirred  for  a  minute,  and  then  decanted  or  filtered. 
The  chloride  is  then  estimated  in  the  filtrate  in  the  usual 
manner.  The  addition  of  ferrous  sulphate  gets  rid  of  the 
organic  matter  which  is  carried  down  with  the  ferrous  carbonate 
precipitate,  and  so  gives  a  neutral  solution  in  which  the  hydrogen 
peroxide  will  not  exert  any  reducing  action  on  the  chromate ; 
also,  it  precipitates  the  arsenic  and  copper  present  in  the  gases 
from  copper  works.  The  potassium  permanganate,  added  to 
oxidise  the  organic  matter,  must  be  employed  with  caution, 
since  the  manganese  sulphate  produced  may  reduce  the 
chromate,  with  production  of  a  green  coloured  solution  ;  this 
will,  however,  not  occur  if  the  solutions  are  neutralised  as 
described. 

Should  any  of  the  difficulties  above  referred  to  be  met  with, 
it  is  best  to  oxidise  with  nitric  acid  and  estimate  the  chloride 
by  Volhard's  method  (employing  ammonium  thiocyanate  for 
titration). 

A  continuous  test  may  of  course  be  made,  as  in  the  case 
of  the  exit-gases  of  the  sulphuric  acid  process  (infra,  p.  337), 
by  employing  a  large  aspirator  and  selecting  a  suitable  type 
of  absorption  apparatus. 

2.  Gases  evolved  in  the  Har greaves  Process. — By  this  process, 
sodium  chloride  contained  in  large  iron  cylinders  is  directly 
converted  into  sulphate  by  drawing  the  gases  from  pyrites  kilns, 
together  with  steam,  through  the  salt,  whereby  the  sulphur 
dioxide  of  the  gases  is  gradually  absorbed  and  in  its  place 
hydrogen  chloride  is  liberated.  The  progress  of  the  reaction 
must  be  constantly  followed  by  taking  samples  of  the  gases 
passing  through  the  connecting  pipes  between  the  cylinders, 
and  testing  these  as  follows  : — 

(a)  For  total  acidity,  preferably  by  the  method    of  Lunge 
(p.  141). 

(b)  F 'or  sulphur  dioxide ,  by  the  method  of  Reich  (pp.  137,243). 

(c)  For  hydrogen  chloride.     This  is  found  by  titrating   the 
sample,    taken    for   test   (a)    with    silver   nitrate,    either    by 
the   ordinary  method   of  Mohr  and  others,   or   by   Volhard's 
method. 


336  TECHNICAL  GAS-ANALYSIS 

The  content  of  sulphur  trioxide  is  obtained  by  deducting 
b  -f-  c  from  a. 

In  the  daily  practice  it  is  sufficient  to  apply  either  a  or  b, 
but  in  every  case  the  test  (c)  must  be  made. 

A  method  for  detecting  and  estimating  hydrogen  chloride, 
bromide,  or  iodine  in  the  presence  of  hydrogen  cyanide  is  described  by 
Polstorffand  Meyer  (Z.  anal.  Chem.,  1912,  li.  p.  60 1).  A  portion  of 
the  solution,  which  must  not  be  too  concentrated,  is  cooled  down, 
rendered  alkaline,  and  formic  aldehyde  added,  with  agitation, 
until  the  smell  is  strongly  felt.  If  now  nitric  acid  is  added,  the 
presence  of  halogenides  is  found  on  addition  of  silver  nitrate. 
For  their  quantitative  estimation,  first  the  cyanogen  contents 
are  ascertained  by  Liebig's  method ;  then  about  06  of  the 
substance  is  dissolved  in  100  c.c.  water,  the  solution  rendered 
alkaline,  20  or  30  drops  of  35  per  cent,  formic  aldehyde  solution 
added,  after  a  few  minutes  acidulated  with  nitric  acid,  and  the 
halogen  contents  estimated  by  Volhard's  method. 

EXAMINATION  OF  GASES  IN  THE  MANUFACTURE  OF 
SULPHURIC  ACID  BY  THE  LEAD-CHAMBER  PROCESS. 

We  must  distinguish  the  following  three  cases  : — 

1.  Gases  before  entering  into   the  Chambers. — This   extends 
merely  to  their  content  of  sulphur  dioxide,  sometimes  also  of 
sulphur  trioxide ;  and  is  mostly  carried  out  by  the  method  of 
Reich,   as   modified   by  Lunge  (supra,  p.    141).     Cf.   also   the 
methods  described,  pp.  243  et  seq. 

2.  Gases  of  the  Lead  Chambers  (  Vitriol  Chambers). — These 
are  generally  only  examined   by  observing  the   colour  (more 
particularly  in  the  back-chambers  and  in  getting  out),  the  tem- 
perature, and  the  pressure  under  which  they  stand.     A  chemical 
analysis   of  these   gases   is   generally   not   made,   and    under 
ordinary  working   conditions   but   little   advantage   would   be 
derived  from  it,  owing  to  the  difficulty  of  obtaining  really  average 
samples ;  moreover,  it  is  unnecessary  since  the  process  is  con- 
trolled by  analysing  the  inlet-  and  exit-gases  (Nos.  I  and  3).     If 
exceptionally  such  an  analysis  has  to  be  made,  it  can  be  carried 
by  the  methods  described  infra  for  the  investigation  of  the  exit- 
gases.     For  more  exact  determinations,  which  do  not  enter  into 
the  ordinary  sphere  of  technical  gas-analysis,  we  refer  to  the 


VITRIOL  CHAMBER  GASES  337 

methods  employed  by  Lunge  and  Naef  (Chem.  hid.,  1884,  PP-  5 
et  seq.)  and  Trautz  (Z.  physik.  Chem.,  1904,  p.  526).  We  also 
refer  to  the  method  of  Raschig  for  the  estimation  of  these  gases 
for  sulphur  dioxide  and  nitrous  compounds  (supra,  p.  244). 

3.  Exit-gases  from  the  Gay-Lussac  Towers — (a)  Estimation 
of  free  oxygen. — This  is  the  most  important  factor  for  regulating 
the  working  of  the  chambers  in  general,  and  the  damper  in  the 
outlet  pipe  in  particular. 

The  oxygen  is  estimated  by  absorbing  it,  and  measuring  the 
resulting  decrease  in  volume.  The  various  methods  employed 
for  this  purpose  have  been  described  in  detail  supra,  pp.  119 
and  211.  We  especially  recommend  the  employment  of  moist 
phosphorus  in  very  thin  sticks,  which  is  much  less  trouble- 
some and  expensive  than  that  of  pyrogallol.  It  must,  however, 
be  remembered  that  phosphorus  is  not  acted  upon  by  oxygen 
at  temperatures  below  15° ;  therefore,  if  the  apparatus  is  standing 
in  a  cold  place,  the  absorption  vessel  must  be  slightly  warmed. 
Since  the  water  with  which  the  phosphorus  is  moistened  would 
also  absorb  the  acids  contained  in  the  gas,  this  must  be 
passed  through  caustic  potash  solution  before  absorbing  the 
oxygen. 

Where,  as  usual,  only  several  tests  are  made  in  the  course  of 
the  day,  the  use  of  a  special  aspirator  is  unnecessary ;  the  gas- 
burette  itself  may  be  used  as  such  by  filling  and  emptying  it 
three  or  four  times  in  succession  from  the  opening  in  the  gas 
main  provided  for  taking  samples.  It  is,  however,  advisable  to 
make  a  continuous  test,  in  addition  to  the  above,  by  drawing  the 
gas  slowly  during  the  full  twenty-four  hours  into  a  vessel  from 
which  the  sample  for  analysis  is  taken.  For  this  purpose 
an  aspirator  of  wood  or  metal  may  be  employed,  if  the  acid 
vapours  are  previously  removed  from  the  gases,  which  is  suitably 
done  in  connection  with  the  absorbing  apparatus.  On  the 
other  hand,  more  simple  apparatus  may  be  used,  provided  they 
permit  at  least  10  litres  of  the  gas  to  be  passed  through  and 
measured  during  the  twenty-four  hours,  in  order  to  obtain  a 
really  representative  average  sample. 

The  estimation  of  oxygen  by  means  of  moist  phosphorus  is 
conveniently  carried  out  in  an  Orsat  apparatus,  pp.  66  et  seq., 
with  two  absorbing  vessels,  one  of  which  is  charged  with  caustic 
potash  solution  for  the  absorption  of  acids,  the  other  with  very 

Y 


338 


TECHNICAL  GAS-ANALYSIS 


thin  sticks  of  moistened  phosphorus.  The  manipulation  is 
described  eodem  loco.  A  very  convenient  form  of  apparatus, 
devised  by  Strype  for  the  analysis  of  exit-gases,  is  described  in 
Lunge's  Sulphuric  Acid  and  Alkali ',  3rd  ed.,  i.  p.  739. 
Other  apparatus  have  been  described,  e.g.,  by  Davis  (Chem. 
News,  1880,  xli.  p.  1 88);  Lovett  (/.  Soc.  Ghent.  Ind.,  1882,  p. 
no);  Pringle  (ibid.,  1883,  p.  53).  We  here  show  the  apparatus 
of  Lindemann,  as  modified  by  Cl.  Winkler,  Fig.  125.  The 
measuring-tube  A  is  fitted  at  the  top  with  a  three-way  tap,  and 


FIG.  125. 

has  a  capacity  of  100  c.c.,  of  which  25  c.c.  are  contained  in  the 
lower  cylindrical  portion,  which  is  graduated  in  TV  c.c.  B 
is  the  absorption  vessel  filled  with  thin  rods  of  phosphorus,  and 
C  the  levelling  bottle.  The  manipulation  is  the  same  as  with 
the  Orsat  apparatus. 

M.  Liebig  (Post's  Chem.  Tech.  Analyse,  2nd  ed.,  i.  p.  700) 
describes  an  apparatus  arranged  for  absorbing  the  oxygen  by 
alkaline  pyrogallol ;  the  gas  is  aspirated  by  means  of  a  rubber 
bellows  into  a  50  c.c.  pipette,  and  forced  from  this  through  the 
absorbing  solution  into  a  graduated  measuring-tube. 


GAY-LUSSAC  EXIT-GASES  339 

(b)  Examination  for  Acids. — If  only  the  sulphur  dioxide 
remaining  in  the  exit-gases  is  to  be  estimated,  this  cannot  be 
done  by  the  original  Reich's  method,  owing  to  the  presence  of 
nitrogen  oxides,  but  by  Raschig's  modification  of  that  method 
(p.  244).  Or  else  a  measured  volume  of  the  gases  is  drawn 
through  sodium  hydroxide  solution,  which  is  afterwards 
strongly  diluted  with  water  and  poured  into  chlorine-  or 
bromine- water.  This  liquid  is  acidified  with  hydrochloric  acid, 
heated  to  boiling,  and  barium  chloride  added.  Each  I  g.  of 
the  precipitated  barium  sulphate  indicates  93-77  c.c.  SO2  of 
o°  and  760  mm. 

A  complete  examination  of  the  exit-gases  may  be  carried  out 
as  follows : — On  the  one  hand  the  sum  of  the  sulphur  acids  is 
determined,  on  the  other  hand  the  sum  of  the  nitrogen  acids, 
irrespective  of  the  degree  of  oxidation.  The  following  scheme 
agrees  in  the  main  with  that  adopted  by  the  British  Alkali 
Makers'  Association  in  1878;  improvements  have,  however, 
been  made  in  details  (abridged  from  Lunge-Keane's  Technical 
Methods,  etc.,  i.  p.  336). 

A  small  volume  of  gas  is  drawn  continuously  from  the  Gay- 
Lussac  exits  by  means  of  a  constant  aspirator,  at  such  a  rate 
that  at  least  24  cb.  ft.  (  =  0-68  cb.m.)  are  collected  in  the 
twenty-four  hours.  The  volume  V  drawn  off  is  corrected  in  the 
way  indicated  supra,  p.  17,  to  o°  and  760  mm.,  and  the  corrected 
volume  called  V1.  The  gas  is  drawn  through  four  absorption 
bottles,  each  holding  100  c.c.,  and  containing  a  column  of  liquid 
at  least  75  mm.  deep.  The  opening  of  the  inlet  tubes  should 
not  exceed  0-5  mm.,  as  measured  by  a  standard  wire.  The 
first  three  bottles  each  contain  100  c.c.  of  normal  sodium 
hydroxide  solution,  free  from  nitre,  the  fourth  100  c.c.  of 
distilled  water.  After  the  passage  of  the  gases,  the  contents 
of  the  four  bottles  are  combined,  the  bottles  washed  out  with 
a  small  volume  of  water,  and  the  total  is  divided  into  three 
equal  parts,  one  portion  being  kept  as  a  reserve.  The  first 
portion  is  titrated  with  normal  sulphuric  or  hydrochloric  acid, 
which  gives  a  measure  of  the  total  acidity  (SO2,  H2SO4,  N2O3, 
and  HNO3).  The  second  portion  is  added  gradually  to  such  a 
quantity  of  a  warm  solution  of  potassium  permanganate, 
rendered  strongly  acid  by  sulphuric  acid,  that  a  slight  excess  of 
permanganate  remains,  which  is  finally  neutralised  by  a  few 


340  TECHNICAL  GAS-ANALYSIS 

drops  of  sulphurous  acid  solution  up  to  the  point  that  only  a 
faint  rose  tint  remains.  All  the  nitrogen  acids  are  now  present 
as  nitric  acid,  no  excess  of  sulphurous  acid  being  in  the  solution. 
The  HNO3  is  estimated  by  the  well-known  method  of  pouring 
it  into  25  c.c.  of  a  solution  containing  100  g.  crystallised  ferrous 
sulphate  and  100  g.  pure  sulphuric  acid  per  litre,  to  which  20  to 
25  c.c.  pure  concentrated  sulphuric  acid  has  been  added,  the 
operation  being  performed  in  a  flask  into  which  CO2  is  passed, 
the  second  tube  of  the  stopper  being  luted  with  water  ;  the 
flask  is  heated  to  boiling,  and  this  is  continued  until  the 
solution,  which  at  first  is  dark-coloured  owing  to  the  nitric 
oxide  present,  has  turned  bright  yellow.  The  ferrous  salt 
remaining  unoxidised  by  the  nitric  acid  is  retitrated  with  N\2 
permanganate  solution,,  equivalent  to  0-004  g«  oxygen  per  I  c.c. 
The  strength  of  the  acid  ferrous  sulphate  solution  is  compared 
each  day  with  that  of  the  permanganate  solution.  If  x  c.c. 
normal  acid  are  used  in  the  first  titration  (for  total  acids), 
y  c.c.  permanganate  for  retitrating  the  unoxidised  ferrous  salt, 
and  z  c.c.  permanganate  are  equivalent  to  25  c.c.  of  the  ferrous 
sulphate  solution,  the  figures  required  are  obtained  by  the 
following  equations  (the  volume  V1  being  measured  in  cubic 
metres  or  in  cubic  feet)  : 

(1)  Total  acidity  expressed  in  grammes  SO3  per  cubic  metre  = 

0.120(100-.*:) 

~Vr~ 

„  „  in  grains  SO3  per  cubic  foot  = 

1.852(100-  jg) 
V1 

f  \    0  7i7  ,.  0.008(600  -  6x  -  z  +  y) 

(2)  Sulphur  \\\  grammes  per  cubic  metre  =  -     —  ^  -  —^  —  -  ", 

grains         „         foot        =  0.12346(600-  6*-«+jQ 

(3)  Nitrogen  in  grammes    „         metre     =  °' 


grains        „         foot        = 


Frantz  (Z.  physik.  Chem.,  1904,  p.  526)  objects  to  this 
method  that,  owing  to  the  action  of  oxygen  and  sulphur 
dioxide  on  the  strongly  alkaline  solution  of  nitrate  and  nitrite, 


GAY-LUSSAC  EXIT-GASES  341 

there  is  a  formation  of  sulphate,  sulphite,  salts  of  sulpho-nitric 
acids,  and  nitrogen  protoxide,  whereby  too  little  nitrogen 
oxides,  an  inexact  figure  for  total  acids,  and  too  much  nitrogen 
is  found. 

In  most  cases,  in  the  place  of  the  method  just  described, 
it  is  sufficient  to  determine  the  total  acidity  of  the  gases  by 
titrating  with  decinormal  sodium  hydroxide  solution  and 
phenolphthalein,  either  by  means  of  the  absorbing  bottle  of 
Lunge  (p.  324,  Fig.  104),  or  that  of  the  Alkali  Inspectors  (p.  245, 
Fig.  105),  or  a  ten-bulb  tube  (p.  146,  Fig.  72). 

The  maximum  escape  allowed  under  the  English  Alkali 
Act  of  1906  is  the  equivalent  of  4  grains  SO3  per  cubic  foot 
(  =  9.15  g.  per  cubic  metre)  of  exit-gases,  before  they  are  mixed 
with  air  or  smoke.  In  Germany  the  limit  is  5  g.  per  cubic 
metre  when  burning  pyrites,  or  8  g.  in  the  case  of  blende,  all 
acids  being  calculated  as  SO3. 

The  English  Alkali  Inspectors  have  recently  adopted  a  mix- 
ture of  i  vol.  N\2  alkali  and  10  vols.  neutral  hydrogen  peroxide 
for  the  absorption  of  acid  gases.  This  overcomes  the  difficulty 
caused  by  secondary  reactions  between  sulphites  and  nitrites, 
which  is  liable  to  occur  when  sodium  hydroxide  solution  is 
used  alone  (Carpenter  and  Linder,  /.  Soc.  Chem.  Ind.,  1902, 
p.  1490). 

Watson  (/.  Soc.  Chem.  Ind.y  1903,  p.  1279)  shows  that  the 
highest  figures  for  acids  are  obtained,  if  the  first  absorbing 
vessels  are  charged  with  hydrogen  peroxide  alone,  the  following 
vessels  with  alkaline  hydrogen  peroxide ;  he  attributes  this  to 
the  decomposition  of  certain  nitrogenous  compounds  by  the 
hydrogen  peroxide,  which  are  only  absorbed  by  alkaline 
hydrogen  peroxide. 

(c)  Nitric  Oxide. — This  may  be  still  present  in  the  gases 
after  they  have  passed  through  the  above-described  absorbing 
vessels.    Its  estimation  has  been  described  supra,  pp.  316^  seq. 

(d)  Nitrogen  Protoxide  has   been  found   in  the  exit-gases 
by  Inglis  (/.  Soc.  Chem.  Ind.,  1904,  pp.  690,  778;  1906,  p.  149; 
1907,  p.  668),  and  by  Hempel  (Z.  Elektrochem    1906,  p.  600). 
The  methods  for  estimating  this  gas  by  combustion  have  been 
described,   p.   314,  but  these   are  only   applicable  where  it  is 
present  in  somewhat  considerable  proportions.     The  extremely 
slight  quantities  of  N2O  present  in  the  Gay-Lussac  exit-gases 


342  TECHNICAL  GAS-ANALYSIS 

were  determined  by  Inglis  by  cooling  the  gases  with  liquid  air, 
fractionating  the  liquid  at  the  lowest  possible  temperature, 
preventing  any  secondary  reactions,  and  avoiding  indirect 
analysis.  His  method  showed  much  smaller  proportions  of 
N2O  than  the  similar  process  of  Hempel,  whose  method  was 
more  indirect;  it  showed  at  most  10  per  cent,  of  the  loss  of 
nitrogen  to  be  in  this  form.  These  methods  for  estimating 
very  little  N2O  in  the  presence  of  large  proportions  of 
N,  O,  CO2,  nitrous  gases,  and  SO2  require  such  complicated 
apparatus  and  so  much  manipulative  skill  that  they  are  outside 
of  the  domain  of  technical  gas-analysis. 

(e)  Loss  of  Sulphur  in  the  Exit-gases.  —  Lunge  (Dingl.pofyt.f., 
1877,  ccxxvi.  p.  634;  Sulphuric  Acid  and  Alkali,  4th  ed.,  vol.  i. 
p.  986)  has  drawn  up  a  formula  which  allows  the  quantity  of 
sulphur  burnt,  expressed  in  grammes  per  litre  on  the  exit-gases, 
to  be  calculated  from  the  percentage  volume  of  oxygen  in  these 
gases.  The  loss  of  sulphur  may  be  calculated  by  comparing 
this  value  with  the  quantity  of  sulphur  acids  present  in  the 
exit-gases.  The  formula  is  : 


where  x  signifies  the  total  sulphur  burnt  expressed  in  grammes 
per  litre  on  the  exit-gas,  a  the  percentage  volume  of  oxygen  in 
the  exit-gas,  t  its  temperature,  and  h  the  pressure. 

Chlorine. 

Free  chlorine  in  gaseous  mixtures  can  be  estimated  in 
various  ways,  mostly  indicated  in  former  chapters,  e.g.,  by 
absorption  in  a  concentrated  solution  of  ferrous  chloride  which 
absorbs  the  chlorine  rapidly  and  in  quantity,  leaving  air  and 
carbon  dioxide  behind  ;  the  unchanged  ferrous  chloride  is 
retitrated  by  standard  permanganate,  or  by  a  solution  of 
arsenious  acid  in  sodium  carbonate  solution,  retitrating  with 
decinormal  iodine  solution  and  starch  as  indicator,  in  which 
case  the  hydrogen  chloride  present  at  the  same  time  can  be 
estimated  as  well  (cf.  p.  136). 

The  analysis  of  gases  containing  a  large  percentage  of 
chlorine,  e.g.,  those  evolved  in  the  Deacon  process,  cannot  be 
carried  out  by  absorption  in  sodium  hydroxide  solution 


CHLORINE  343 

followed  by  titration  for  "available"  and  total  chlorine,  since  it 
is  impossible  to  avoid  the  formation  of  chlorate.  This  difficulty 
has  been  overcome  by  the  following  method,  worked  out  in  the 
laboratory  of  Messrs  Gaskell,  Deacon  &  Co.  (Lunge's  Sulphuric 
Acid  and  Alkali,  3rd  ed.,  vol.  iii.  p.  470)  : — 

Aspirate  5  litres  of  the  gas,  leaving  the  decomposer,  through 
250  c.c.  of  a  sodium  hydroxide  solution  of  sp.  gr.  1-075,  divided 
between  two  or  three  bottles,  to  absorb  both  HC1  and  free 
chlorine.  Unite  the  contents  of  the  bottles,  dilute  to  500  c.c., 
and  test  as  follows  : 

(1)  One  hundred  c.c.  of  the  solution  are  heated  to  boiling 
with  25  c.c.  of  a  solution  of  100  g.  ferrous  sulphate  and  100  pure 
concentrated  sulphuric  acid  in  I  litre  of  water,  the  heating  being 
performed  whilst  excluding  the  air  from  the  flask  by  a  Bunsen 
valve  or  Contat  bulb.     When  cold,  the  contents  of  the  flask  are 
diluted  with  200  c.c.  of  water,  and  titrated  with  N\2  permanganate 
solution.      The  number  of  cubic   centimetres   so   required   we 
put=jj>,  and  the  number  of  cubic  centimetres  of  permanganate 
necessary  to  oxidise  the  25  c.c.  of  ferrous  sulphate  solution  =  x. 

(2)  A  small  volume  of  sulphur  dioxide  solution  is  added  to 
10  c.c.  of  the  above  alkaline  solution,  and  the  mixture  acidified 
with  dilute  sulphuric  acid,  so  that  there  is  a  distinct  smell  of 
SO2.     The  acidified  solution  is  heated  to  boiling,  allowed  to 
cool,  a  few  drops  of  permanganate  solution  added,  if  necessary, 
to   oxidise   any   remaining   sulphurous    acid,   after  which   the 
solution  is  neutralised  with  pure  sodium  carbonate  and  titrated 
with  N/io  silver  nitrate  solution,  employing  neutral  potassium 
chromate  as  indicator,     z  signifies  the  number  of  cubic  centi- 
metres of  silver  solution  required.    The  percentage  decomposition 
of  the  hydrochloric  acid  gas  is  then  found  by  the  expression 

^ — ,  and  the  volume  of  air  per  I  vol.  of  HC1  by 

43.53+^ 


Should  some  other  volume  of  gas,  »,  be  evaporated  instead  of 
5  litres,  the  constant,  43-53,  must  be  altered  to        *  0-003645 
assuming  that  the  remaining  operations  are  carried  out  exactly 


344  TECHNICAL  GAS-ANALYSIS 

as  above,  and  that  i  litre  HC1  at  o°  and  760  mm.  weighs 
1-624  g. 

Younger  (J.  Soc.  Chem.  Ind.,  1889,  p.  88)  prefers  the  following 
method :  He  passes  the  gas  through  a  solution  of  arsenious 
acid,  and  employs  an  aspirator  which  gives  the  weight  of  chlorine 
in  unit  volume  of  the  gases  directly.  The  percentage  of  HC1 
in  the  gas  is  determined  by  titrating  the  reacting  solution  with 
silver  nitrate.  The  absorption  is  effected  in  a  cylinder  con- 
taining 100  c.c.  of  an  aqueous  solution 
of  arsenious  acid,  each  i  c.c.  of  which 
corresponds  to  0-15432  grains  (  =  001  g.) 
chlorine.  The  charged  cylinder  is  con- 
nected with  the  bottle  B  (Fig.  126), 
containing  about  i  g.  potassium  iodide 
dissolved  in  water ;  the  arsenious  acid 
solution  is  coloured  blue  by  a  very  small 
quantity  of  indigo-carmine.  A  cubic 
foot  (  =  0-0283  cb.m.)  in  capacity  of  the 
aspirator  C  is  divided  into  any  con- 
venient number  of  parts,  e.g.,  1 12.  One 
side  of  the  gauge-glass  D  is  calibrated 
to  give  the  grains  of  chlorine  per  cubic 
foot  of  gas,  and  the  corresponding 
volume  of  gas  aspirated  is  given  on 
the  other  side  of  the  same  lines.  The 
liberation  of  iodine  from  the  potassium 
iodide  solution,  and  the  simultaneous 

bleaching  of  the  indigo-carmine,  indicate  the  completion  of  the 
test;  when  this  occurs,  the  aspiration  is  interrupted,  and  the 
readings  taken.  The  HC1  is  determined  by  titrating  10  c.c. 
of  the  arsenious  acid  solution  with  NJIQ  silver  nitrate  solution. 
Should  the  gases  be  free  from  HC1,  the  silver  nitrate  necessary 
for  titration  will  be  28-2  c.c.,  this  volume  corresponding  to  the 
HC1  derived  from  the  chlorine  absorbed.  Any  volume  over 
and  above  this  28-2  c.c.  corresponds  to  the  HC1  present  as  such 
in  the  gases.  The  way  of  calculating  the  results  is  illustrated 
by  a  special  example  in  Lunge-Keane's  Technical  Methods,  etc., 
vol.  i.  p.  489.) 

For  estimating  very  slight  quantities  of  chlorine  in  the  air 
of  certain  chemical  manufactures,  or  in  that  of  their  surroundings, 


CHLORINE 


345 


a  large  quantity  of  this  air  is  drawn  through  15  to  20  c.c.  of  a 
freshly  prepared  colourless  solution  of  potassium  iodide,  and 
then  through  a  vessel  containing  decinormal  sodium  thiosulphate 
solution.  In  presence  of  free  chlorine  (or  bromine)  the  potas- 
sium iodide  solution  is  coloured  brown  by  the  liberated  iodine. 
The  solution  is  washed  into  a  beaker,  and  the  iodine  titrated 
with  N/io  or  N/ioo  sodium  thiosulphate;  I  c.c.  Njio sodium 
thiosulphate  indicates  3-545  mg.  chlorine  (or  7-996  mg.  bromine). 
The  quantity  of  iodine  vapour  carried  over  from  the  first 
receiver  into  the  sodium  thiosulphate  receiver  is  determined 


FIG.  127. 

by  titrating  with  N/ioo  iodine  solution,  and  is  added  to  the 
amount  found  in  the  first  receiver. 

Such  an  estimation  is  especially  necessary  before  opening 
bleaching-powder  chambers,  to  prevent  injury  to  the  workmen, 
and  nuisance  in  the  neighbourhood.  Before  opening  the 
chamber,  the  chlorine  present  in  the  air  thereof  must  not  exceed 
5  grains  per  cubic  foot  (=11-5  g.  per  cubic  metre),  as  agreed  to 
by  the  manufacturers  more  than  twenty  years  ago,  but  the 
present  practice  is  to  restrict  the  limits  to  2j  grains  per  cubic 
foot. 

The  determination  of  the  chlorine  present  in  the  chamber 
atmosphere  may  be  carried  out,  e.g.,  by  an  Orsat  apparatus  (p.  66). 
We  here  show  in  Fig.  127  the  simplified  apparatus  described 
by  Fleming-Stark  (/.  Soc.  Chem.  Ind.,  1885,  p.  311).  The 


346  TECHNICAL  GAS-ANALYSIS 

burette  a  is  filled  with  water  and  connected  by  means  of  a 
rubber  tube  with  the  reservoir  b,  a  tap  c  being  inserted  between 
the  two.  This  tap  is  provided  with  two  passages  at  right 
angles  to  each  other,  the  one  of  small  and  the  other  of  large 
diameter.  This  allows  of  a  strong  flow  of  water  when  filling 
the  burette,  and  of  a  diminished  flow  when  the  gas  is  forced 
into  the  absorbing  solutions.  The  four  tubes,  d,  d,  d,  d,  are 
filled  with  an  aqueous  solution  of  potassium  iodide,  and  each 
may  be  connected  through  a  corresponding  glass  tap  with  the 
burette.  Each  absorption  tube  is  provided  with  a  double- 
bored  stopper,  and  a  tube  reaching  almost  to  the  bottom  of 
the  absorption  vessel  passes  through  one  of  these  openings. 
This  tube  is  narrowed  at  its  lower  end,  so  as  to  break  up  the 
gas-bubbles,  and  at  its  upper  end  is  connected  through  the 
tube  e  with  the  bleaching-powder  chamber.  The  tube  passing 
through  the  second  opening  in  the  stopper  is  cut  off  just 
below  the  stopper,  and  serves  to  connect  the  absorbing  vessels 
to  the  burette.  A  small  wash-bottle  containing  potassium 
iodide  solution  and  starch  is  inserted  between  the  absorption 
tubes  and  the  burette.  The  two-way  tap  g,  provided  between 
the  wash-bottle  and  the  burette,  permits  the  air  to  escape 
during  the  filling  of  the  burette  without  passing  through  the 
wash-bottle. 

In  using  the  apparatus,  387  c.c.  of  gas,  as  measured  in  a, 
are  drawn  through  one  of  the  absorption  tubes  d ;  the  solution 
in  the  wash-bottle  affords  an  absolutely  safe  indication  of  the 
completion  of  the  chlorine  absorption.  The  contents  of  d  are 
then  washed  into  a  beaker,  and  titrated  with  N/io  sodium 
arsenite  solution.  The  grains  of  chlorine  per  cubic  foot  are 
obtained  by  multiplying  by  two  the  number  of  cubic  centimetres 
of  arsenite  solution  so  required. 

The  Government  Alkali  Inspectors  make  use  of  the  simple 
apparatus  shown  in  Fig.  128.  A  is  an  ordinary  rubber  pressure 
ball,  provided  with  a  small  hole  B  in  the  mouth-piece.  The 
end  of  this  passes  through  one  of  the  two  holes  in  the  cork  C ; 
a  glass  tube  D,  bent  at  right  angles,  passes  through  the  second. 
This  latter  tube  reaches  nearly  to  the  bottom  of  the  cylinder  E, 
and  is  narrowed  down  at  the  lower  end  so  that  only  a  very 
fine  needle  can  be  inserted.  The  cylinder  E  is  filled  with  the 
solution  described  below,  and  the  outer  end  of  D  is  inserted 


CHLORINE 


347 


in  an  opening  in  the  bleach  at  a  height  of  2  ft.  above  the  floor. 

To   take   a  sample  of  the  chamber  gas,  A  is  compressed,  the 

hole   B   being   covered  by  the  finger,  and   the  pressure  then 

released  ;  by  the  expansion  of  the  bulb  the  gas  in  the  chamber 

is   drawn   through   the   tube   D   and  the   solution  in  E.     The 

operation  is  repeated  until  the  solution  in  E  becomes  coloured 

by  the  separation  of  iodine,  and  the  number  of  aspirations  to 

cause  this  is  noted.     Each  delivery  of  the  bulb  corresponds  to 

4  oz.  (about   100  c.c.)  or  ^TJ-  of  a   cubic   foot.     The   solution 

employed  is  prepared  by  dissolving  0-3485  g. 

of    arsenious    acid     in     sodium     carbonate, 

neutralising  with  sulphuric  acid,  adding  25  g. 

potassium  iodide,  2  g.   precipitated   calcium 

carbonate,  6   to    10  drops  of  ammonia,  and 

diluting  the  whole  to  I  litre;  26  c.c.  of  the 

solution  are  employed    for  each   test,  and  a 

little  starch  solution   is  added  as  indicator. 

Under  these  conditions  five  deliveries  of  the 

bulb  will  produce  a  coloration  when  the  gas 

contains  5  grains  of  chlorine  per  cubic  foot, 

ten  deliveries  when  the  chlorine  content   is 

only  2\  grains  per  cubic  foot,  and  so  on. 

Orthotoluidine  is  recommended  as  a  re- 
agent for  the  colorimetric  estimation  of  small 
quantities  of  free  chlorine  by  Ellms  and 
Hauser  (/".  Ind.  and  Eng.  Chem.,  1913, 
p.  915;  Chem.  Zentralb.,  1914,  i.  p.  72).  Fio.  128. 

They  prepare  the  reagent  by  dissolving  one- 
tenth  per  cent,  of  orthotoluidine  in  a  10  per  cent,  solution 
of  hydrochloric  acid.  The  reagent  does  not  deteriorate  on 
standing.  It  produces  with  small  quantities  of  chlorine  a 
yellow  colour,  regardless  of  the  soluble  constituents  of  the 
water  to  be  tested.  The  alkalinity  of  the  water  in  no  way 
affects  the  shade  or  tint  produced.  The  presence  of  sulphates, 
chlorides,  and  nitrates  of  the  alkalies  and  alkaline  earths  does 
not  interfere  with  the  test.  The  yellow  colour  develops  in 
about  three  minutes  and  is  permanent  for  at  least  half  an  hour. 
In  this  way  0-005  part  per  million  of  free  chlorine  can  be 
detected.  There  is  a  good  gradation  of  colour  for  increasing 
amounts  of  free  chlorine. 


348  TECHNICAL  GAS-ANALYSIS 

Estimation  of  Carbon  Dioxide  in  Chlorine  Gas. 

This  estimation  is  very  important,  both  in  gas  produced 
by  the  Deacon  process,  and  in  that  produced  by  electrolytical 
methods,  since  carbon  dioxide,  if  present  to  any  appreciable 
amount,  renders  the  manufacture  of  high-strength  bleaching- 
powder  impossible.  Electrolytic  chlorine  sometimes  contains 
up  to  12  per  cent,  of  carbon  dioxide  proceeding  from  the 
carbon  electrodes. 

Hasenclever  (Winkler's  Industrie-Case,  ii.  p.  368)  passes 
a  measured  volume  of  the  gas,  previously  freed  from  hydrogen 
chloride  by  bubbling  through  a  wash-bottle  containing  water, 
through  an  ammoniacal  solution  of  barium  chloride.  When 
the  absorption  is  complete,  the  solution  is  heated,  the  barium 
carbonate  filtered  off  and  thoroughly  washed  with  boiled 
water.  The  washed  precipitate  is  either  ignited  and  weighed 
or  dissolved  in  hydrochloric  acid,  and  the  barium  precipitated 
as  sulphate.  One  g.  BaSO4  corresponds  to  0-1885  g.  CO2. 

According  to  Sieber  (Chem.  Zeit.,  1895,  p.  1963)  this  method 
is  only  applicable  to  gases  containing  not  more  than  10  per 
cent,  of  chlorine,  a  condition  always  satisfied  by  Deacon  gases. 
In  the  case  of  more  concentrated  gases,  like  electrolytic  chlorine, 
the  method  is  unsuitable,  owing  to  the  solubility  of  barium 
carbonate  in  barium  chloride.  The  object  of  boiling  the 
solution  before  filtering  off  the  barium  carbonate  is  to  destroy 
any  carbonate  present  in  the  solution.  The  CO2  can  be  also 
determined  by  absorbing  the  gases  in  sodium  hydroxide 
solution,  destroying  the  hypochlorite  formed  by  addition  of 
sodium  arsenite,  and  then  liberating  the  CO2  by  addition  of 
sulphuric  acid.  This  necessitates  the  previous  determination 
of  the  CO2  in  the  various  reagents  employed,  and  is  also 
uncertain  when  only  small  amounts  of  CO2  are  present.  Sieber 
therefore  prefers  absorbing  the  gases  in  a  caustic  soda  solution 
of  known  carbonate  content,  decomposing  the  hypochlorite 
by  boiling  with  cobalt  oxide,  adding  sulphuric  acid,  and 
passing  the  liberated  CO2  through  a  solution  of  potassium 
iodide  previously  saturated  with  CO2  and  air,  to  retain  any 
traces  of  chlorine  carried  forward ;  the  purified  CO2  is  then 
absorbed  in  a  cooled  potash  bulb,  and  weighed. 

This  method  is  declared  by  Lunge  (cf.  Lunge-Keane.,  vol.  i.  p. 


CARBON  DIOXIDE  IN  CHLORINE 


349 


492)  to  be  unreliable  for  the  determination  of  small  quantities 
of  carbon  dioxide,  especially  owing  to  the  necessity  of  work- 
ing with  a  solution  of  potassium  iodide  saturated  with  CO2.  It 
is  both  simpler  and  more  accurate  to  absorb  the  gas  in  sodium 
hydroxide  solution,  to  decompose  the  hypochlorite  by  boiling 
with  ammonia,  and  then  to  estimate  the  CO2  either  by  liberat- 
ing the  gas  or  by  the  barium  chloride  method. 

Ferchland   (Z.  Elektrochem.,  1906,  p.  114)   takes  away  the 
chlorine   by  metallic    mercury  and   then 
estimates   the  CO2   by   absorption    in   a 
solution  of  potassium  hydrate. 

Philosophoff  (Chem.  Zeit.,  1907,  pp. 
959  and  1256;  Lunge  and  Berl,  Chemisch- 
technische  Untersuchungsmethoden,  i.  p. 
584)  gives  special  instructions  for  carrying 
out  this  process  in  a  convenient  manner. 

Tread  well  in  his  Analytical  Chemistry \ 
6th  ed.,  vol.  ii.  p.  694,  describes  a  method 
for  estimating  the  carbon  dioxide  in 
electrolytical  chlorine,  consisting  in  ab- 
sorbing both  chlorine  and  carbon  dioxide 
by  a  solution  of  sodium  hydroxide, 
measuring  the  residue,  and  titrating  the 
hypochlorite  formed  in  the  alkaline  solu- 
tion by  means  of  sodium  arsenate,  the 
difference  representing  the  carbon  dioxide. 
This  method  gives  too  low  results,  as 
appreciable  quantities  of  chlorate  are 
formed  in  the  absorption  of  the  chlorine. 
Hence  Treadwell  and  Christie  (Z.  angew. 
Chem.,  1905,  p.  1930)  have  modified  the  process  as  follows: — 
In  Fig.  129,  B  is  a  Bunte  burette,  which  is  thoroughly  dried 
before  making  a  determination.  The  chlorine  gas  to  be 
examined  is  dried  by  means  of  a  calcium  chloride  tube,  and  is 
allowed  to  flow  through  B  for  from  five  to  ten  minutes  before 
closing  the  taps.  Then  the  lower  three-way  tap  a  is  closed, 
then  the  upper  two-way  tap  b,  and  the  state  of  the  thermometer 
and  barometer  noted.  Now  tap  a  is  connected  by  the  rubber 
tube  with  the  levelling-tube  N,  filled  with  a  sodium  arsenite 
solution  free  from  carbonate.  This  solution  is  prepared  by 


FIG.  129. 


350  TECHNICAL  GAS-ANALYSIS 

dissolving  4-95  g.  of  arsenious  oxide  in  dilute  potassium 
hydroxide  solution,  adding  phenolphthalein,  exactly  neutralis- 
ing with  sulphuric  acid,  and  diluting  to  I  litre.  One  hundred 
c.c.  of  this  decinormal  solution  are  introduced  into  the  burette 
through  tap  a  to  absorb  the  chlorine,  and  subsequently  10  c.c.  of 
a  i  :  2  potassium  hydroxide  solution  through  the  funnel  above  b, 
whereby  the  CO2  is  absorbed.  The  residue  of  unabsorbed  gas 
(nitrogen,  oxygen,  and  carbon  monoxide)  as  a  rule  amounts  to 
0-5  to  I  per  cent.  After  taking  the  readings,  the  solutions  and 
washings  are  collected,  phenolphthalein  is  added,  and  the 
whole  neutralised  with  hydrochloric  acid  ;  60  c.c.  of  sodium 
bicarbonate  solution  (35  g.  per  litre)  are  then  introduced, 
and  the  excess  of  arsenite  solution  titrated  with  N/io  iodine 
solution  and  starch.  One  c.c.  N/io  arsenite  solution  consumed 
=  0-003546  g.  chlorine,  or  1-1016  c.c.  chlorine  at  o°  and  760  mm. 
The  carbon  dioxide  is  found  by  the  difference  between  the 
chlorine  and  the  sum  of  C1  +  CO2  previously  found. 

Lunge  and  Offerhaus  (Z.  angew.  Ckem.,  1903,  p.  1033)  pass 
the  gas  to  be  analysed  through  two  Bunte  burettes  placed  in 
series.  The  gas  contained  in  one  of  the  burettes  is  treated 
with  sodium  hydroxide  solution,  to  absorb  both  chlorine  and 
carbon  dioxide,  and  the  residue  measured.  The  gas  in  the 
other  burette  is  treated  with  a  potassium  iodide  solution  in 
order  to  take  up  the  chlorine,  which  is  determined  by  titrating 
the  liberated  iodine  with  standard  arsenite  or  thiosulphate 
solution  as  above.  They  also  describe  another  method,  in 
which  only  one  burette  is  required  for  this  determination, 
which  has  been  modified  by  Tread  well  and  Christie  (ibid.,  1905, 
p.  1930)  as  follows  : — 

The  chlorine  is  absorbed  by  a  5  per  cent,  solution  of 
potassium  iodide,  then  the  carbon  dioxide  by  10  c.c.  potassium 
hydroxide  solution,  and  the  total  volume  of  absorbed  gas 
determined.  The  excess  of  KOH  converts  the  liberated  iodine 
into  iodide  and  iodate.  The  liquid  from  the  apparatus  is  then 
run  into  a  beaker  containing  10  c.c.  of  strong  hydrochloric 
acid,  and  the  liberated  iodine  titrated  with  thiosulphate.  The 
results  are  accurate,  but  the  method  presents  no  advantage  over 
the  arsenite  method  as  described  above. 

Lunge  and  Rittener  (ibid.,  1906,  p.  1853)  absorb  the  chlorine 
in  a  Bunte  burette  by  a  N/io  solution  of  sodium  arsenite  and 


IMPURITIES  OF  ATMOSPHERIC  AIR  351 

then  the  CO2  by  sodium  hydroxide ;  the  unchanged  arsenite  is 
titrated  back,  and  the  CO2  obtained  by  difference  from  the 
volume  of  total  absorbable  gases  found.  The  details  of  this 
method  are  also  given  in  Lunge-Keane's  Technical  Methods,  etc., 
vol.  i.  p.  514. 

Nourrisson  (Chem.  Zeit.,  1904,  p.  107)  examines  such 
impure  chlorine  in  an  Orsat  apparatus  by  first  absorbing 
the  chlorine  by  stannous  chloride,  then  the  carbon  dioxide  by 
sodium  hydroxide,  and  finally  the  oxygen  by  metallic  copper 
and  ammonia  solution. 

Schloetter  (Z.  angew.  Chem.,  1904,  p.  301)  absorbs  the 
chlorine  by  hydrazinc  sulphate,  whereby  each  2  vols.  of  chlorine 
liberate  I  vol.  of  nitrogen,  and  subsequently  the  carbon 
dioxide  by  sodium  hydroxide  solution. 

Detection  and  Estimation  of  Free  Bromine  and  Chlorine. 

Deniges  and  Chelle  (Bull.  Soc.  Chim.,  1913,  xiii.  p.  626) 
employ  an  aqueous  solution  of  magenta  (rosaniline  hydro- 
chloride),  decolorised  by  dilute  sulphuric  acid,  and  mixed  with 
the  same  volume  of  acetic  acid.  This  reagent  is  coloured 
yellow  by  chlorine,  and  purple  by  bromine.  The  coloured 
compounds  formed  can  be  extracted  by  chloroform.  Their 
spectra  are  greatly  different.  This  reaction  allows  of  a  colori- 
metric  estimation  of  traces  of  free  chlorine  and  bromine,  in 
solution  or  in  the  state  of  vapour.  (This  process  is  an  improve- 
ment of  that  described  by  Deniges  in  Ann.  Chim.  anal., 
1913,  p.  8,  where  test  paper  soaked  in  a  magenta  solution, 
decolorised  by  bisulphite  and  acidified  by  weak  hydrochloric 
acid,  is  employed.) 

Impurities  occurring  in  Atmospheric  Air. 

Apart  from  the  normal  constituents,  oxygen  and  nitrogen, 
atmospheric  air  always  contains  various  impurities  in  the  shape 
of  gases,  vapours,  mist,  and  dust.  The  determination  of  some 
of  these  has  been  already  described  in  previous  chapters ; 
e.g.,  dust  and  soot,  p.  112;  liquid  admixtures  (incl.  moisture),1 

1  The  moisture  contained  in  atmospheric  air  is  usually  estimated,  not 
by  chemical  methods,  but  by  the  physical  method  of  "  psychrometry," 
which  does  not  belong  to  the  sphere  of  technical  gas-analysis. 


352  TECHNICAL  GAS-ANALYSIS 

p.  115  ;  carbon  dioxide,  pp.69,  89,96,  107,  136,  142,  222  ;  ozone, 
p.  220;  hydrogen  peroxide,  p.  221.  Numerous  impurities  may, 
moreover,  get  into  the  air  by  industrial  operations,  e.g.,  carbon 
monoxide,  pp.  89,  109,  239;  sulphur  dioxide,  pp.  135,  142  et  seq., 
243  et  seq.\  hydrogen  chloride,  pp.  136,  145;  chlorine,  p.  136; 
hydrogen  sulphide,  p.  147;  carbon  disulphide,  p.  314;  inflam- 
mable gases  and  vapours,  p.  316;  nitroglycerine,  p.  314; 
nitrogen  oxides  and  acids,  p.  314  et  seq. ;  ammonia,  p.  325; 
hydrogen  cyanide,  p.  328. 

In  this  place  we  treat  of  some  impurities  carried  into  the 
air  by  specific  chemical  industries,  apart  from  those  already 
treated  (mostly  after  Lunge-Keane's  Technical  Methods,  vol.  i. 
pp.  903  et  seq.\ 

Phosphorus  Trichloride. — Butjagin  (Arch.  f.  Hygiene,  xlix.) 
passes  the  air  to  be  examined  through  a  solution  of  sodium 
hydroxide,  and  estimates  the  sodium  chloride  formed  by  the 
reaction:  PCl3+3NaOH  =  P(OH)8+3NaCl. 

Fluohydric  and  Hydrofluosilicic  Acid. — Traces  of  these  acids 
occur  in  the  air  near  aluminium  works  in  which  aluminium 
fluoride  is  used.  This  subject  is  treated  in  detail  in  a  paper 
by  H.  Wislicenus  (Z.  angew.  Chem.,  1901,  pp.  701  et  seq.),  but 
he  directed  his  efforts  to  the  proof  of  the  presence  of  fluorine 
compounds  in  the  ashes  of  the  plants  affected  by  such  air, 
without  indicating  a  mode  for  testing  for  them  in  the  air  itself, 
which  is  evidently  a  matter  of  extreme  difficulty.  Where  it  is  the 
question  of  testing  gases  for  large  quantities  of  those  acids, 
and  other  acids  are  not  present,  or  are  separately  estimated, 
the  acidity  of  the  gases,  as  determined  by  absorption  in  caustic 
alkali  solution,  with  phenolphthalein  as  indicator,  is  a  measure 
for  them.  Fellner  (Chem.  Zeit.,  1895,  p.  1143)  points  out  that 
the  solution  must  be  boiled,  otherwise  the  results  are  too  low. 

Hydrogen  Phosphide,  H8P,  an  extremely  poisonous  gas,  occurs 
sometimes  in  slight  traces  in  the  air  of  laboratories  or  of 
factories.  It  can  be  detected  by  means  of  paper  soaked  with 
silver  nitrate,  which  is  thereby  blackened  by  the  secretion  of 
metallic  silver,  phosphoric  acid  being  formed.  Its  estimation 
when  present  as  an  impurity  in  commercial  acetylene  has  been 
described  supra,  p.  1 50. 

Hydrogen  phosphide  can  be  estimated,  according  to  Lunge 
(Z.  angew.  Chem.,  1897,  p.  651),  by  passing  the  gases  through 


MERCURY  VAPOUR  353 

bromine  water  or  a  solution  of  sodium  hypochlorite,  and 
precipitating  the  phosphoric  acid  thereby  formed  by  magnesia 
mixture.  If  a  silver  solution  is  employed  for  absorbing  it,  the 
excess  of  silver  must  be  first  precipitated  by  hydrochloric  acid. 
One  mg.  P2O5  =  o-48  mg.  H3P. 

According  to  Riban  (Comptes  rend.,  Ixxxviii.  p.  581), 
hydrogen  phosphide  is  absorbed  by  a  solution  of  cuprous 
chloride  in  hydrochloric  acid.  Yokote  (Arch.f.  Hygiene,  xlix.) 
estimates  it  by  passing  a  large  volume  of  the  air  either  through 
nitric  acid  or  through  bromine  water,  and  determining  the  phos- 
phoric acid  formed  in  the  usual  way.  Volumetric  methods  are 
not  applicable. 

Hydrogen  Arsenide,  H3As. — This  gas  is  detected  in  the  air 
by  its  characteristic  garlic-like  smell  even  when  present  in 
minute  quantities ;  or  by  passing  the  air  through  a  solution  of 
silver  nitrate,  which  is  thereby  darkened.  Such  a  darkening 
is,  of  course,  equally  produced  by  hydrogen  sulphide  or 
phosphide.  The  same  reagent  can  serve  for  the  quantitative 
estimation  of  that  gas,  by  precipitating  the  excess  of  silver  with 
hydrochloric  acid,  and  determining  the  arsenic  in  the  filtrate 
as  Mg2As2O7. 

2AsH3+i2AgNO3  +  3H.2O  =  As2O3+  i2HNO3+  i2Ag. 


Mercury  Vapour. 

We  have  already  in  a  former  place  (p.  115)  mentioned  the 
detection  of  this  impurity  in  air  by  the  grey  coloration  imparted 
to  gold  leaf,  and  its  quantitative  estimation  by  the  same 
reaction. 

Kunkel  and  Fessel  (  Verh.  d.  phys.-med.  Gesellsch.,  Wiirzburg, 
xxxii.  p.  i)  pass  the  dry  air  through  a  tube,  2  to  3  mm.  wide 
and  25  cm.  long,  slightly  bent  in  the  middle,  containing  a  few 
particles  of  iodine ;  a  deposit  of  red  or  reddish-yellow  mercuric 
iodide  is  formed  just  beyond  the  iodine,  if  any  mercury  vapour 
is  present  in  the  air,  and  its  quantity  may  be  approximately 
gauged.  The  air  should  not  pass  through  the  tube  at  a  greater 
rate  than  I  litre  in  from  eight  to  ten  minutes. 

In  order  to  estimate  the  mercury  vapour  quantitatively,  the 
mercuric  iodide,  deposited  as  above,  is  dissolved  in  potassium 

z 


354  TECHNICAL  GAS-ANALYSIS 

iodide,  filtered  from  any  particles  of  solid  iodine  present,  and 
sufficient  sodium  hydroxide  added  to  the  filtrate  to  combine 
with  any  free  iodine.  The  mercury  is  then  determined  colori- 
metrically  in  the  shape  of  the  black  sulphide  by  adding 
ammonium  sulphide  to  the  solution,  and  comparing  the  colour 
produced  with  that  imparted  to  faintly  alkaline  solutions  of 
mercuric  chloride  on  similar  treatment ;  or  the  mercury  may  be 
deposited  by  electrolysis  and  weighed  (Lehmann,  Arch.  f. 
Hygiene,  xx.).  The  maximum  quantity  of  mercury  vapour 
which  can  be  present  in  I  cb.m.  of  air  at  o°  is  approximately 
2  mg. ;  at  10°,  6  mg. ;  at  20°,  14  mg.  ;  at  30°,  31  mg. 


Ether  Vapour. 

This  vapour  may  be  absorbed  quantitatively  from  an 
enclosed  volume  of  air  by  sulphuric  acid  of  sp.  gr.  1-84  in  about 
thirty  minutes,  and  may  thus  be  determined  volumetrically 
(Horwitz,  Dissertation,  Wiirzburg,  1900). 

Mercaptan. 

Rubner  (Arch.  f.  Hygiene,  xix.  p.  156)  recommends  as  a 
qualitative  test  the  grass-green  coloration  imparted  by 
mercaptan  to  porous  earthenware  soaked  with  a  solution  of 
isatin  in  sulphuric  acid  ;  the  air  should  be  dried  over  calcium 
chloride,  and  then  passed  through  tubes  containing  the  pieces 
of  earthenware.  First  a  green,  and  then  a  bluish-green  colour 
is  produced.  A  quantitative  determination  in  air  is  scarcely 
practicable ;  when  lead  nitrate  is  used  as  an  absorbent,  quantita- 
tive results  are  only  obtained  if  very  precise  conditions  are 
observed  in  regard  to  the  concentration  of  the  solution 
employed. 

Aniline  Vapour. 

Lehmann  (loc.  tit.)  passes  the  air  to  be  tested  for  aniline 
through  two  absorption  vessels  in  series,  containing  10  per  cent, 
sulphuric  (not  hydrochloric  !)  acid,  neutralises  the  bulk  of  the  acid 
and  titrates  the  solution  with  bromine  solution,  the  strength  of 
which  has  been  determined  with  potassium  iodide  and  sodium 


GASES  PRODUCED  ON  A  LARGE  SCALE  355 

thiosulphate.  The  bromine  solution  is  prepared  by  dissolving 
3  to  4  g.  bromine  in  I  litre  of  water,  and  adding  sodium 
hydroxide  until  the  colour  of  the  solution  is  changed  from 
brown  to  yellow.  The  bromine  forms  with  aniline,  tribrom- 
aniline.  The  reaction  is  : 


3Br2  +  C6H5NH2  =  C6H2Br3.  NH2  +  3HBr. 

One  c.c.  of  N/io  bromine  solution  =  -^  =  1-55  mg.  aniline. 

/ 

Tobacco  Smoke. 

Pontag  (Z.  Unters.  Nahr.  u.  Genussm.,  1903,  p.  646 ; 
Lunge -Keane,  Technical  Methods,  etc.,  p.  910)  aspirates  the 
smoke,  first  through  caustic  soda  solution,  then  through  sul- 
phuric acid,  and  estimates  therefrom  the  hydrocyanic  acid  and 
the  nicotine,  pyridine,  and  ammonia  ;  also  the  carbon  monoxide. 
As  this  subject  does  not  exactly  belong  to  technical  gas- 
analysis,  we  refer  to  the  above-stated  publications. 

The  injurious  effects  of  the  impurities  of  air,  both  on  account 
of  the  diminution  they  cause  in  the  percentage  of  oxygen,  and 
of  their  direct  poisonous  action,  on  health  and  vegetation,  are 
described  in  Lunge- Keane,  loc.cit.,  i.  pp.  908  et  seq.,  according  to 
the  investigations  of  Lehmann  and  of  Haldane,  founded  on 
Government  Reports. 

Arndfs  air-tester  (Ger.  Ps.  Nos.  241074  and  247165  ; 
J.  Gasbeleucht.,  1913,  p.  407)  shows  the  admixture  of  a  certain 
gaseous  impurity  by  the  change  of  colour  of  a  body  impregnated 
with  a  test  solution. 


ANALYSIS    OF    GASEOUS    MIXTURES    PRODUCED 
ON   A   LARGE   SCALE. 

In  the  preceding  chapters  we  have  discussed  all  the 
methods  applied  in  technical  gas-analysis  for  the  examination 
of  gaseous  mixtures  produced  on  a  large  scale.  In  this  place 
we  shall  merely  enumerate  the  constituents  present  in  such 


356  TECHNICAL  GAS-ANALYSIS 

mixtures,  and  indicate  the  places  where  the  analytical  methods 
for  them  are  described.  The  methods  for  taking  proper 
samples  of  these  gases  have  been  described  on  p.  3  et  seq. 

i.  Fire-gases  (Smoke-gases -,  Furnace-gases}. 

Soot,  p.  112. 

Carbon  dioxide,  pp.  69,  89,  96,  107,  136,  142,  222. 

Carbon  monoxide,  pp.  89,  109,  239. 

Combustible  gases,  p.  309. 

Sulphur  dioxide,  pp.  135,  142,  143. 

Oxygen,  pp.  55,  64,  69,  89,  152,  211. 

2.  Producer-gases  (including  Water-gas),  Dowson  Gas,  etc, 

Carbon  monoxide,  pp.  89,  109,  239. 

Hydrogen,  pp.  71,  90,  97,  109,  129,  152,  156,  167,  266. 

Methane,  pp.  71,  109,  152,  266. 

Heavy  hydrocarbons,  pp.  117,  304. 

Total  combustible  gases,  pp.  155,  164. 

Carbon  dioxide,  pp.  69,  89,  96,  107,  136,  142,  222. 

Oxygen,  pp.  55,  64,  69,  89,  152,  211. 

3.   Coal-gas  (Illuminating  Gas).1 

Carbon  monoxide,  pp.  89,  109,  239. 

Hydrogen,  pp.  71,  90,  97,  109,  129,  152,  156,  167,  266. 

Methane,  pp.  71,  109,  152,  266. 

Acetylene,  pp.  118,  132,  147,  281. 

Ethylene,  pp.  109,  119,  167,  286. 

Naphthalene  vapour,  p.  289. 

Heavy  hydrocarbons,  pp.  117,  304. 

Benzene,  pp.  108,  167,  288. 

Total  combustible  gases,  pp.  155,  164. 

Carbon  dioxide,  pp.  69,  89,  96,  107,  136, 142,  222. 

Oxygen,  pp.  55,  64,  69,  89,  152,  211. 

Hydrogen  sulphide,  pp.  147,  150. 

1  An  historical  study  on  the  development  of  the  analysis  of  illuminating 
gas  has  been  published  by  Czako  in/.  Gasbeleucht.^  1913,  pp.  1192  et  seq. 


COMPRESSED  AND  LIQUEFIED  GASES  357 

Carbon  disulphide  and  other  sulphur  compounds,  p.  147. 

Total  sulphur,  pp.  149,  245,  247. 

Tar  vapours,  p.  305. 

Ferrocarbonyl,  p.  313. 

Ammonia,  p.  325. 

Cyanogen  and  compounds  of  it,  p.  328. 

Illuminating  power,  p.  210. 

Specific  gravity,  p.  178. 

Calorific  power,  p.  190  (according  to  Chem.  Trade  /.,  1914. 
p.  522,  the  House  of  Lords  Committee  has  decided  that  in 
future  the  calorific  value  of  the  gas  supplied  to  the  customers 
shall  be  the  only  standard  for  its  value). 


COMPRESSED   AND    LIQUEFIED   GASES.1 

I.  GENERAL  RULES. — Such  rules  on  the  storage,  carriage, 
sampling,  etc.,  are  contained  in  a  document,  communicated  by 
the  Prussian  Minister  of  Commerce  to  the  German  Verein  zur 
Wahrungder  Interessen  derchemischen  Industrie,  and  published 
in  Chem.  Ind.,  1904,  pp.  689  et  seq. 

The  following  gases  are  found  in  trade  in  the  compressed  or 
liquefied  state :  Carbon  dioxide,  ammonia,  chlorine,  sulphur 
dioxide,  carbon  oxychloride  (phosgen),  nitrogen  protoxide, 
acetylene,  marsh-gas  (methane),  coal-gas  (including  similar 
illuminating  gases),  hydrogen,  oxygen,  nitrogen  and  atmos- 
pheric air. 

The  original  contains  detailed  descriptions  of  the  vessels 
(bottles)  serving  for  keeping  and  transporting  these  com- 
pressed or  liquefied  gases.  These  vessels,  when  filled,  must 
not  be  thrown  about,  and  should  be  protected  against  con- 
cussions of  any  kind ;  they  must  not  be  exposed  to  direct 
sunlight  or  other  sources  of  heat,  or  to  air  of  a  temperature 
exceeding  40°. 

1  This  chapter  is  principally  founded  on  the  corresponding  chapter  in 
Lunge  and  Beri's  Chemisch-technische  Untersuchungsmethoden^  6th  ed., 
1910,  i.  pp.  638  et  seq.  The  following  special  publications  treat  of  this 
matter  :  Teichmann,  Komprimierte  und  verfliissigte  Gase,  Halle,  1908 ; 
and  Urban,  Laboratiumsbuch  fur  die  Industrie  der  verfliissigten  und 
komprimierten  Case,  Halle,  1909. 


358 


TECHNICAL  GAS-ANALYSIS 


The  following  table  shows  the  properties  and  conditions 
of  carriage  of  the  more  important  liquefied  and  compressed 
gases :— 


Gas, 
liquefied  or 
compressed. 

Sp.  gr. 

Vapour  tension. 
Atmospheres. 

Boiling- 
point 
at 
760  mm. 

Fus  ing- 
point. 

Critical 
tempera- 
ture. 

0°. 

15°. 

30°. 

0°. 

15°. 

30°. 

°C. 

°C. 

XL 

S02 

NH3 

1-435° 
0-6341 

I-3964 
0-6138 

0-5918 

1-53 
4-19 

2-72 
7-14 

4-52 

-     IO-I 

-  38-5 

-    76 

-    75 

155-4 
130-0 

C!2  . 
C02 

1-469 
0-947 

I-4257 
0-864 

f-3799 
0-732 

3-66 
36-  1 

5-75 
52-16 

8.8 
73-8 

-    33-6 
-   78-2 

-102 

-    57 

146-0 
3I-I 

N20 

o-937 

0-870 

36-1 

49-8 

68-0 

-   87-9 

-102 

35-4 

COCL 

+       8-2 

H2  . 

-2^2 

" 

-  234.1; 

02   . 

mym 

-183 

-  1  1  8«o 

*     3 

Conditions  of  carriage  on  German 

Ik.  on 

railways. 

Gas, 
liqaefied  or 
compressed. 

Critical 
pressure. 

Sp.  gr. 
at  0°  and 
760  mm. 
air  =  1 

Litre 
weight 
atO° 
and 
760  mm. 

being 
liquefied 
yields  gas 
at  0°  and 
760  mm. 

Official 
examination 
pressure. 

Space 
required 
for  1  kg. 

Repetition 
of  the 
examination 
of  pressure 

required  after 

Atmospheres. 

Litres. 

Atmospheres. 

Litres 

years. 

S02 

NH3 

78.9 

2-264 
0-597 

2-9266 
0-7719 

342 
1290 

12 

30 

0-8 
1-86 

2 

4 

C12. 

93-5 

2-490 

3-2I9I 

310-5 

22 

0-8 

2 

C02 

73 

1-5291 

1-9768 

508-9 

190 

1-34 

4 

N2() 

75 

I-5298 

1-9777 

506 

1  80 

1-34 

4 

COC!2 

3p 

0-8 

2 

H2. 

20 

0-0696 

0-08998 

... 

{the  full  I 

4 

02   . 

50 

1-1055 

1-4292 

... 

strength  j 

4 

II.  SAMPLING. — In  most  cases  it  is  advisable  to  place  the 
bottles  horizontally  before  sampling.  The  bottles  filled  with 
such  a  liquid,  when  some  of  the  gas  has  been  taken  out, 
have  a  gas  space  above  the  liquid  the  composition  of  which 
is  not  identical  with  the  average  composition  of  the  liquid. 
Thus,  e.g.t  when  analysing  liquid  carbon  dioxide,  there  is 
an  essential  difference  between  the  samples  drawn  from 
vertically  or  horizontally  placed  bottles.  Werder  (Chem.  Zeit.> 
1906,  p.  1021),  when  analysing  an  inferior  quality  of  liquid 
carbon  dioxide,  found  on  taking  the  sample  (a  from  a 
bottle  in  the  upright  position  72  per  cent,  (U)  from  a  bottle 


COMPRESSED  AND  LIQUEFIED  GASES  359 

lying  on  its  side  94  per  cent.  CO2 ;  in  the  case  of  very  good 
qualities  he  found  (#)  92  per  cent.,  (b)  98-8  per  cent. ;  in  the  case  of 
a  first-class  article  (a)  99  per  cent.,  (V)  99-85  per  cent.  An  analysis 
from  a  partly  emptied  bottle  does  not  indicate  the  average 
composition  (cf.  Woy,  Chem.  Zentralb.,  1904,  ii.  p.  1072,  and 
Wentzki,  ibid.,  p.  1763). 

In  the  case  of  compressed  or  liquefied  gases,  standing  under 
very  high  pressure,  it  is  advisable  to  employ  a  reducing-valve  for 
sampling.  In  order  to  remove  all  the  air  from  it,  the  gas 
should  pass  for  at  least  ten  to  fifteen  minutes  in  a  rapid  current 
through  the  reducing-valve.  In  order  to  prevent  the  analytical 
apparatus  from  being  smashed,  Thiele  and  Deckert  (Z.  angew. 


FIG.  130.  FIG.  131. 

Chem.,  1907,  p.  737)  warmly  recommend  interposing  between 
the  gas-bottle  in  this  apparatus  a  glass  Tee-piece,  the  descend- 
ing branch  of  which  dips  into  mercury.  If  the  pressure  in  the 
apparatus  exceeds  that  of  the  mercury  column,  the  excess  of 
gas  escapes  through  the  mercury  into  the  air. 

The  sampling  of  liquefied  gases  can  be  in  many  cases 
advantageously  performed  by  the  pipette  of  Bunte  and  Eitner 
(/.  Gasbeleucht.,  1897,  p.  174,  Figs.  130  and  131).  On  the  lateral 
pipe  of  the  bottle,  which  is  placed  in  a  horizontal  or  slanting 
position,  a  thin  brass  tube  is  fixed  by  means  of  a  screw  cap.  At 
the  other  end  of  this  tube  there  is  a  brass  disc,  M,  with  a  leather 
or  rubber  washer,  G.  In  order  to  firmly  connect  this  tube  with 


360  TECHNICAL  GAS-ANALYSIS 

the  pipette,  the  latter  is  provided  at  the  top  with  a  glass  ring, 
W,  ground  flat,  which  can  be  pressed  against  G  by  means  of 
a  removable  clamp  with  screw  wings.  The  pipette  holds 
70  c.c.,  and  is  closed  at  top  and  bottom  by  well  ground-in 
glass  taps,  which  are  not  very  conical,  as  they  are  in  this  case 
less  easily  forced  out  of  the  bores.  For  sampling  liquid 
ammonia  they  are  greased  with  castor  oil.  The  pipette  is 
accurately  weighed  on  a  chemical  balance  and  fixed  in  the 
above-indicated  manner  to  the  gas-bottle.  Then  both  taps  are 
opened,  in  order  to  drive  out  the  air  from  the  pipette.  Now 
the  outer  tap  is  closed,  and  by  opening  the  valve  of  the  gas- 
bottle,  the  liquefied  gas  is  forced  into  the  pipette  until  this  is 
two-thirds  full.  It  is  recommended  to  put  on  gloves  and 
protecting  spectacles,  to  provide  against  the  squirting  about  of 
liquefied  gas  on  loosening  the  taps.  When  the  filling  has  been 
done,  first  the  valve  of  the  gas-bottle  is  shut,  then  the  second 
tap  of  the  pipette,  which  is  then  taken  off  and  weighed,  so  as 
to  learn  the  quantity  of  liquefied  gas  enclosed. 

3.  Measuring  the  Gas. — For  this  purpose  any  of  the  gas- 
burettes  previously  described  may  be  employed,  such  as  the 
Bunte  burette  (p.  58),  the  Orsat  apparatus  (p.  66),  and  Hempel's 
apparatus  (p.  82).  For  testing  liquid  carbon  dioxide  or 
chlorine,  the  most  convenient  apparatus  is  the  "modified 
Winkler's  burette  "  (p.  84). 

As  confining  liqiiids  are  employed :  water,  or  saturated 
solutions  of  salt  (taking  notice  of  the  solubility  of  the  gases  in 
water,  supra,  p.  31),  or  for  more  exact  determinations  mercury, 
in  such  cases  where  it  is  not  acted  upon  by  the  gas  to  be  tested. 
For  chlorine  we  do  not  yet  possess  any  suitable  confining 
liquids. 

Apparatus  for  examining  Gaseous  Impurities,  not  absorbed  by 
the  proper  Absorbing  Liquid  for  the  Gas  under  Estimation. — 
Special  contrivances  have  been  described  by  Treadwell 
(Quant.  Analyse,  4th  ed.,  p.  606);  Thiele  and  Deckert 
(Z.  angew  Chem.,  1907,  p.  737) ;  Franzefi  (Z.  anorg.  Chem.,  1908, 
Ivii.  p.  395);  Stock  and  Nielsen  (Blrl.  Ber.,  1906,  p.  3389). 
Treadwell's  apparatus  is  shown  in  Fig.  132.  The  thick-walled 
flask  A,  holding  about  I  \  litres,  is  charged  with  500  c.c.  of  the 
absorbing  reagent,  and  the  absorbing  tube  with  tap  H  is 
fixed  air-tight  in  it.  By  sucking  at  H,  the  absorbing  tube  is 


LIQUEFIED  SULPHUR  DIOXIDE 


361 


IT 


entirely  filled  with  absorbing  liquid,  whereupon  H  is  closed. 
The  Greiner-Friedrichs  patent  tap,  I,  is  now  turned  into  position 
II,  and  by  sucking  at  its  left-hand  outlet  pipe 
the  entrance  pipe  is  filled  with  absorbing  liquid 
up  to  the  plug  of  the  tap.  Now  the  tap  is 
turned  into  position  I,  gas  is  passed  on  from 
the  iron  bottle  until  the  air  has  been  com- 
pletely displaced,  and  the  tap  is  put  into 
position  II,  whereupon  the  gas  enters  into  the 
absorbing  tube.  The  non-absorbable  gaseous 
constituents  collect  below  H.  Gas  is  passed 
into  the  apparatus  until  70  to  80  c.c.  non- 
absorbable  gases  have  been  obtained,  which 
are  driven  over  into  a  Hem  pel  burette  or  other 
convenient  apparatus,  and  analysed  in  the 
ordinary  way. 


FIG.  132. 


III.  ANALYSIS  OF  THE  VARIOUS  DESCRIPTIONS  OF 
COMPRESSED  GASES. 

(i)  Liquefied  Sulphur  Dioxide. 

The  essential  impurities  present  in  this  are  :  water,  sulphuric 
acid,  lubricating  oil,  air,  sometimes  also  carbon  dioxide. 

In  order  to  test  for  water,  sulphuric  acid,  and  lubricating 
oil,  a  good-sized  sample  of  the  liquid  is  taken  by  means  of  the 
Bunte-Eitner  pipette,  p.  359.  This  pipette  is  then  placed 
upright  in  a  large  beaker,  connected  with  weighed  calcium 
chloride  tubes,  and  by  opening  the  tap  on  the  side  of  the 
absorbing  tubes  the  SO2  is  made  to  evaporate.  When  most 
of  it  has  evaporated,  the  pipette  is  placed  horizontally  in  an 
air-bath,  heated  to  70°,  and  the  last  remainder  of  volatile 
substances  is  forced  through  the  absorbing  tubes  by  means  of 
a  carefully  dried  current  of  air.  The  increase  of  weight  of  these 
tubes  shows  the  percentage  of  water,  which  is  especially 
important  where  the  sulphur  dioxide  is  to  be  employed  for 
ice-producing  machines,  for,  according  to  Lange  (Z.  angew. 
Chem.,  1899,  pp.  275,  300,  595),  a  product  containing  water  acts 
strongly  on  the  steel  valves  of  the  compressors,  especially  at 
temperatures  above  70°,  with  formation  of  ferrous  sulphite 
thiosulphate. 


362  TECHNICAL  GAS-ANALYSIS 

The  non-volatile  residue  remaining  in  the  Bunte-Eitner 
pipette  consists  of  sulphuric  acid  and  lubricating  oil.  In  order 
to  estimate  the  sulphuric  acid>  the  pipette  is  rinsed  with 
distilled  water,  heated  in  order  to  remove  the  last  traces  of 
sulphuric  acid,  and  the  sulphuric  acid  titrated  with  standard 
alkali  and  methyl  orange.  The  lubricating  oil  is  obtained  from 
the  residue  by  extraction  with  ether,  filtering  the  extract,  and 
drying  at  100°. 

Any  air  present  n  the  product  is  found  by  the  apparatus 
of  Treadwell,  or  of  Thiele  and  Deckert  (p.  360),  and  identified 
by  the  ordinary  methods  of  gas-analysis.  The  non-absorbed 
gases  may  also  contain  a  great  portion  of  the  carbon  dioxide 
present.  In  order  to  estimate  this  more  correctly,  the  gas  is 
sucked  through  wash-bottles  containing  potassium  dichromate 
solution,  acidified  by  sulphuric  acid.  Here  the  sulphur  dioxide 
is  oxidised  and  retained,  carbon  dioxide  and  air  escape,  are 
dried  by  calcium  chloride,  and  the  CO2  is  absorbed  in  a  weighed 
potash-bulb  apparatus  or  by  soda-lime. 

In  the  case  of  liquid  sulphur  dioxide,  employed  in  the 
manufacture  of  foodstuffs  (e.g.,  for  saturating  sugar  solutions), 
sometimes  a  qualitative  test  for  arsenic  is  called  for.  This  can 
be  performed  by  boiling  the  evaporation  residue  with  sulphuric 
acid  until  all  the  SO2  has  been  expelled,  and  testing  the  liquid 
in  the  Marsh  apparatus. 

In  order  to  directly  estimate  the  SO2,  the  gas  is  passed  into 
a  Bunte  burette  (p.  58),  or  a  modified  Winkler  burette  (p.  84) ; 
a  measured  volume  of  decinormal  iodine  solution  is  allowed  to 
go  in,  the  burette  shaken  until  the  oxidation  is  complete,  its 
contents  run  into  an  Erlenmeyer  flask,  rinsing  several  times 
with  water,  and  the  excess  of  iodine  retitrated  by  N/io 
thiosulphate  solution.  Each  cubic  centimetre  of  N/io  iodine 
solution  consumed  corresponds  to  1-0946  c.c.  of  dry  SO2 
at  o°  and  760  mm. 

A  French  patent,  No.  435763,  of  the  Comp.  Ind.  des  Proc. 
R.  Pictet  describes  an  apparatus  for  the  volumetric  analysis 
of  liquefied  gases,  especially  sulphur  dioxide. 

2.  Liquefied  Ammonia. 

According  to  Lange  and  Hertz  (Z.  angew.  Ckem.,  1897, 
p.  224),  this  may  contain  water,  pyridine  and  its  homologues, 


LIQUEFIED  AMMONIA  363 

benzene,  acetonitrile,  ethyl  alcohol,  naphthalene,  ammonium 
carbonate,  and  pyrrol ;  also  lubricating  oil  from  the  compressors 
as  a  mechanical  impurity. 

In  order  to  ascertain  the  quantity  of  residue  remaining  after 
the  volatilisation,  which  is  in  most  cases  the  only  test  required, 
Lange  and  Hertz  employ  the  following  simple  method : — A 
glass  tube  of  30  to  50  mm.  width  is  continued  into  a  narrow 
tube  of  about  5  mm.  width,  holding  at  least  i-i  c.c.  (Fig.  133). 
The  tube  holds  altogether  about  100  c.c.  ;  up  to  a  mark  in  the 
upper  part  49  c.c.,  corresponding  to  33-3  g.  liquid  ammonia.  In 
the  lower,  narrow  portion  i-i  c.c.  is  divided  in  15  parts,  so  that 
each  part  corresponds  to  02  per  cent.  NH3,  assuming  the 
specific  gravity  of  liquid  ammonia  at  — 38°  =0-68, 
and  that  of  the  residue  =  0-9.  At  the  bottom  a 
piece  of  glass  rod  is  fused  on,  so  that  the  tube  can  be 
placed  in  a  wooden  stand  or  into  the  valve  cap  of  the 
iron  bottle. 

In  order  to  take  a  sample,  the  iron  bottle  is 
placed  in  a  horizontal  position  and  a  small  steel- 
tube  screwed  on  to  the  valve.  Now  the  valve  is 
opened,  and  liquid  ammonia  is  run  into  the  sample 
tube  up  to  the  mark,  which  should  take  about  one 
minute.  The  sample  tube  is  closed  with  a  nicked 
cork  and  its  contents  allowed  to  evaporate  spon- 
taneously, which  takes  about  three  hours.  When  the 
ice  formed  thereby  has  thawed  off,  and  no  more  gas 
bubbles  rise  from  the  narrow  tube,  the  volume  of 
the  residue  in  the  narrow  tube  is  read  off.  Each  division 
indicates  0-2  per  cent.  This-  method  yields  rather  too  high 
results,  for  in  taking  the  sample  a  little  ammonia  evaporates,  so 
that  the  impurities  relatively  increase,  and  in  the  case  of  much 
water  being  present,  some  NH3  remains  in  the  residue.  These 
errors  are  partly  compensated  by  the  fact  that  during  the 
evaporation  of  the  ammonia  part  of  the  impurities  also 
volatilises. 

In  order  to  estimate  the  pyridine  as  well  as  the  ammonia,  a 
sample  of  the  liquid  ammonia  is  taken  in  the  Bunte-Eitner 
pipette  (p.  359).  To  the  pipette,  partially  filled  with  the  liquid 
ammonia,  two  Peligot  tubes,  charged  with  normal  sulphuric 
acid,  are  joined,  and  by  opening  the  intermediate  tap  of  the 


364  TECHNICAL  GAS-ANALYSIS 

pipette,  ammonia  is  passed  through  these  receivers,  where  it  is 
retained  by  the  sulphuric  acid.  In  order  to  drive  over  the 
last  portions  of  ammonia,  at  the  end  of  the  operation  a  current 
of  air  is  passed  through  the  apparatus.  The  sulphuric  acid  is 
diluted  to  1000  c.c.,  and  the  ammonia  and  pyridine  determined 
in  this  liquid.  For  this  purpose  so  much  of  the  acid  liquid  is 
measured  off  that  it  contains  about  1-7  to  2  g.  NH3,  diluted 
with  water  and  titrated  with  normal  ammonia  and  methyl 
orange,  until  the  colour  has  just  passed  into  pure  yellow.  The 
liquid,  whose  volume  is  now  about  250  c.c.,  is  distilled  in  a  flask 
with  cooler  during  half  an  hour,  the  lower  end  of  the  cooler 
dipping  into  30  c.c.  of  water.  All  the  pyridine  and  acetonitrile, 
together  with  some  ammonia,  is  now  in  the  distillate  (A).  To 
this  a  few  drops  of  phenolphthalein  are  added,  and  it  is  titrated 
with  normal  hydrochloric  acid,  which  indicates  the  ammonia 
quite  sharply,  as  pyridine  is  quite  neutral  to  phenolphthalein. 
When  the  liquid  in  the  distilling  flask  has  completely  cooled 
down  caustic  liquor  is  added,  and  the  ammonia,  now  set  free,  is 
distilled  into  normal  acid,  which  is  then  retitrated.  The  acid 
now  consumed,  together  with  that  consumed  in  the  first  distilla- 
tion, indicates  the  quantity  of  ammonia ;  I  c.c.  normal 
hydrochloric  acid  =  0-01703  g.  NH3. 

In  the  first  distillate  (A)  the  ammonia  is  exactly  neutralised, 
a  few  drops  of  a  I  per  cent,  solution  of  patent  blue,  brand  V.N., 
is  added,  and  it  is  titrated  with  N\2  hydrochloric  acid  until  the 
colour  changes  from  pure  blue  into  greenish-blue.  This  test  is 
recommended  by  Milbauer  and  Stanek  (Z.  anal.  Chem.,  1904, 
p.  215),  who  employ  the  following  mode  for  the  estimation  of 
pyridine.  The  solution  obtained  by  evaporating  the  liquid 
ammonia  into  sulphuric  acid  is  evaporated  nearly  to  dryness, 
put  into  a  separating  funnel,  a  sufficient  quantity  of  freshly 
prepared  solution  of  sodium  bicarbonate  and  the  same  volume 
of  ether  added,  and  the  whole  shaken  for  ten  to  fifteen  minutes 
in  a  mechanical  agitator.  The  ether  is  poured  off,  fresh  ether 
added,  and  the  shaking  continued  for  the  same  time.  The 
united  solutions  of  pyridine  bases  thus  obtained  are  filtered 
through  a  filter  moistened  with  ether,  a  few  drops  of  patent  blue 
solution  added  and  thoroughly  shaken  up  with  an  excess  of 
decinormal  sulphuric  acid.  Sodium  chloride  is  added,  and  the 
liquid  retitrated  with  decinormal  caustic  soda  solution  up  to  the 


LIQUEFIED  CHLORINE  AND  CARBON  DIOXIDE     365 

reappearance  of  the  blue  colour.  It  is  advisable  to  repeat  the 
shaking  out  with  ether  a  third  time,  and  to  convince  one's  self 
by  titration  that  there  is  no  more  pyridine  in  solution. 

The  non-absorbable  gases  are  collected  and  tested  as 
described  on  p.  360. 

3.  Liquefied  Chlorine. 

In  this  product,  which  is  made  almost  exclusively  from 
electrolytic  chlorine,  there  are  found  as  impurities :  air,  carbon 
dioxide,  carbon  monoxide,  and  hydrogen  chloride. 

The  chlorine  gas  is  passed  from  the  iron  stock-bottle  into  a 
Bunte  burette,  or,  preferably,  into  a  modified  Winkler  burette 
(p.  84),  and  the  real  chlorine  contained  in  it  estimated  by  one 
of  the  well-known  processes,  e.g.,  the  potassium  iodide  or  the 
sodium  arsenite  method,  or  by  Ferchland's  mercury  method, 
mentioned  on  p.  349.  The  estimation  of  hydrogen  chloride 
alongside  of  free  chlorine  is  made  by  the  methods  described  (pp. 
136  and  142),  that  of  carbon  dioxide  as  described  (p.  222). 
If  chlorine,  hydrogen  chloride,  and  carbon  dioxide  must  be 
estimated,  all  three,  the  chlorine  is  absorbed  by  mercury  (p.  349), 
hydrogen  chloride  and  carbon  dioxide  by  caustic  potash  solution, 
the  burette  is  emptied,  the  aqueous  liquor  separated  from  the 
mercury  and  the  mercurous-chloride  deposit ;  this  is  washed 
out,  as  well  as  the  burette,  and  the  chlorine  ion  titrated  in  the 
united  solution,  e.g.,  by  Volhard's  method.  One  c.c.  N/io  silver 
nitrate  solution  indicates  2-224  c-c-  hydrogen  chloride  gas 
(at  o°  and  760  mm.).  The  gaseous  remainder  not  absorbed  by 
the  caustic  potash  solution  is  best  collected  in  the  apparatus  of 
Treadwell  or  of  Thiele  and  Deckert  (p.  360) ;  it  consists  of 
oxygen,  carbon  monoxide,  and  nitrogen,  which  are  estimated  as 
usual  in  technical  gas-analysis. 

4.  Liquefied  Carbon  Dioxide. 

In  this  occur :  atmospheric  air,  or  according  to  the  mode 
of  manufacture,  various  mixtures  of  oxygen  and  nitrogen ; 
carbon  monoxide,  more  rarely  hydrogen  sulphide,  sulphur 
dioxide,  empyreumatic  substances ;  moreover :  water,  lubricat- 
ing materials  (glycerin,  vaselin,  or  grease).  Most  of  the 
liquefied  carbon  dioxide  now  found  in  the  trade  need  not  be 


366  TECHNICAL  GAS-ANALYSIS 

tested  for  the  last-named  impurities.  If,  on  evaporating  it, 
glycerin  is  found  in  the  residue,  there  is,  according  to 
Teichmann,  ferrous  bicarbonate  present,  which  imparts  a 
disagreeable  taste  to  the  water  impregnated  with  such  carbon 
dioxide.  On  passing  the  CO2  through  a  strongly  diluted, 
acidified  solution  of  permanganate  or  of  iodine,  these  reagents 
ought  not  to  be  decolorised,  which  would  be  caused  by  sulphur 
dioxide  or  empyreumatic  matters.  The  latter  would  also  be 
found  by  the  brown  coloration  of  concentrated  sulphuric  acid 
on  passing  the  gas  through  it. 

For  a  practical  judgment  on  the  quality  of  commercial 
liquid  carbon  dioxide  it  is  mostly  sufficient  to  estimate  the 
content  of  the  liquid  portion  in  gases  not  absorbable  by  caustic 
potash.  An  enquiry  into  the  air  present  in  the  gaseous  space 
is  mostly  unnecessary.  Only  when  very  accurately  enquiring 
into  the  quality  of  otherwise  equal  samples  also  the  quality 
of  the  CO2  present  in  the  gaseous  space  need  be  examined. 
For  establishing  the  contents  of  air  in  the  gas  taken  from  a 
bottle  it  is  usually  sufficient  to  test  the  carbon  dioxide  in  the 
gas  space  before  and  after  taking  out  the  gas.  The  air- 
contents  of  the  gas  taken  out  will  be  approximately  equal  to 
the  arithmetic  mean  of  both  tests. 

Werder  (Chem.  Zeit.,  1906,  p.  1021)  employs  for  the  analysis 
of  liquid  carbon  dioxide  an  Orsat  apparatus  with  a  measuring- 
tube  of  200  c.c.  capacity  and  three  absorbing-tubes,  one  rilled 
with  caustic  potash  solution,  for  absorbing  CO2 ;  the  second 
with  alkaline  pyrogallol  solution,  for  absorbing  oxygen ;  the 
third  with  ammoniacal  cuprous  chloride,  for  absorbing  carbon 
monoxide.  According  to  the  quantity  of  the  impurities,  the 
measuring-tube  is  filled  from  ten  to  twenty  times,  always 
absorbing  the  CO2  and  testing  the  non-absorbed  residue  for 
oxygen  and  carbon  monoxide.  The  same  author  enumerates 
the  following  rules  for  judging  of  the  quality  of  commercial 
liquefied  carbon  dioxide:  (i)  The  smell  must  be  pure,  not 
empyreumatic  or  irritating.  (2)  The  taste  must  be  purely 
acid.  (3)  The  content  of  CO2,  taken  from  the  bottle  in  a 
horizontal  position,  must  be  at  least  98  per  cent.  (4)  The 
content  of  carbon  monoxide  must  not  be  above  0-5  per  cent. 
(5)  The  gas  must  not  contain  either  sulphurous  or  nitrous 
acid.  (6)  After  passing  it  for  a  quarter  of  an  hour  through 


NITROGEN  PROTOXIDE— HYDROGEN  367 

I  DO  c.c.  of  warm  N/i'JO  permanganate  solution,  acidulated 
with  sulphuric  acid,  there  must  be  sensible  decolorisation.  (7) 
After  passing  the  gas  for  a  quarter  of  an  hour  through  100  c.c. 
of  JV/ioo  silver  nitrate  solution,  acidified  with  nitric  acid,  there 
must  be  no  precipitate  visible. 

For  estimating  the  percentage  of  air  in  liquid  carbon  dioxide 
any  gas-analytical  apparatus  may  be  used.  Lange  (Chem.  Ind., 
1900,  p.  530)  for  this  purpose  employs  a  modification  of  the 
Winkler  gas-burette,  constructed  by  himself  and  Zahn,  and 
shown  supra,  p.  55,  where  also  its  manipulation  is  described. 
Wentzki  (Z.  angew.  Chem.,  1913,  i.  p.  376)  describes  for  this 
purpose  an  apparatus  consisting  of  a  burette  with  two  taps, 
below  which  there  is  a  measuring  vessel  and  two  level-bottles, 
one  of  which  contains  caustic  potash,  the  other  mercury.  The 
bottom  tap  of  the  burette  is  also  connected  with  the  carbon 
dioxide  vessel,  and  a  bubble-counter.  The  apparatus  is 
manufactured  by  Dr  Bachfeld  &  Co.,  of  Frankfurt  a.  M. 

An  investigation  of  the  thermal  properties  of  carbon  dioxide 
at  low  temperatures  (  +  20°  to  —50°  C.)  has  been  made  by 
Jenkin  and  Pye  (Proc.  Roy.  Soc.,  1913,  March;  Chem.  Trade]., 
1913,  Hi.  p.  260). 

5.  Liquefied  Nitrogen  Protoxide. 

This  product  is  sold  especially  for  medical  purposes.  The 
impurities  prejudicial  to  this  employment,  as  nitric  oxide, 
chlorine,  acid  gases,  and  ammonia,  should  be  removed  before 
compression  by  washing  with  ferrous  sulphate  solution,  caustic 
potash,  and  weak  acid.  The  methods  for  estimating  the 
nitrogen  protoxide  itself  have  been  described  supra,  p.  314. 

6.  Compressed  Hydrogen. 

The  essential  impurities  of  electrolytically  produced 
hydrogen  are:  oxygen  (admissible  maximum  content  =  2 
volume  per  cent.)  and  nitrogen.  Hydrogen  produced  in  other 
ways  may  contain  arseniuretted  hydrogen,  carbon  monoxide, 
and  carbon  dioxide.  For  testing  qualitatively  for  arseniuretted 
hydrogen,  Reckleben  and  Lockemann  (Z.  anal.  Chem.,  1908, 
p.  126;  Z.  angew.  Chem.,  1908,  p.  433)  pass  the  gas  through  a 
5  to  10  per  cent,  ammoniacal  silver  nitrate  solution.  In  the 


368  TECHNICAL  GAS-ANALYSIS 

presence  of  AsH3  the  solution  is  blackened  by  precipitated 
silver,  and  the  arsenic  can  be  proved  in  the  solution  by  means 
of  ammonia  as  silver  arsenite. 

7.   Compressed  Oxygen. 

The  commercial  article  may  contain  hydrogen  (admissible 
maximum  content  =  4  volume  per  cent),  carbon  dioxide,  and 
nitrogen.  The  analysis  takes  place  according  to  the  prescrip- 
tions given  in  previous  chapters.  Murschhauser  (Z.  angew. 
Chem.j  1908,  p.  2503)  describes  a  special  apparatus  for  the 
analysis  of  compressed  oxygen  of  high  percentage. 


GAS-VOLUMETRIC  ANALYSIS. 

Gas-volumetric  analysis  comprises  those  operations  in  which 
a  constituent  of  a  solid  or  liquid  substance  is  determined  by 
the  generation  and  measurement  of  a  gas.  In  some  instances, 
air  displaced  by  the  generated  gas  is  measured  instead  of  the 
latter. 

We  now  describe  the  methods  and  apparatus  belonging  to 
this  chapter. 

THE  AZOTOMETER. 

This  instrument  was  designed  by  Knop  in  the  year  1860 
for  the  determination  of  ammonia,  by  the  decomposition  of 
its  salts  with  sodium  hypobromite  and  measurement  of  the 
liberated  nitrogen.  It  has  been  improved  by  P.  Wagner 
(Z.  anal.  Chem.,  1870,  p.  235;  1875,  p.  247).  It  can  also  be 
used  for  other  gas-volumetric  purposes,  in  which  gases  are 
measured  over  water,  as  proposed  by  Baumann  (1890)  and 
others. 

This  apparatus  is  shown  in  Fig.  134.  The  reagent  employed 
is  a  sodium  hypobromite  solution,  prepared  as  follows : — One 
hundred  g.  sodium  hydroxide  are  dissolved  in  water  and  diluted 
to  1-25  litres;  25  c.c.  bromine  is  added,  with  external  cooling 
by  water,  the  whole  well  shaken,  and  finally  cooled.  The  solution 
must  be  kept  in  the  dark  in  a  well-stoppered  bottle.  It  is 
employed  in  the  bottle  A,  on  to  the  bottom  of  which  the  glass 
cylinder  a  is  fused.  This  bottle  stands  in  the  large  glass  vessel, 


AZOTOMETER 


369 


B,  which  serves  for  cooling  A  after  the  decomposition.  A  is 
closed  by  a  tightly  fitting  rubber  stopper,  through  which  passes 
the  glass-tap  tube  /,  which  is  connected  by  the  rubber  tube  e 
to  the  first  of  the  communicating  tubes  c  and  d.  These  tubes 
are  placed  in  the  cylinder  C,  filled  with  water,  and  containing 


FIG.  134. 


also  a  thermometer.  Tube  c  is  a  gas-burette,  holding  50  c.c. ; 
d  is  the  level-tube,  connected  at  the  top  by  a  rubber  tube  with 
glass-tap  g  to  the  supply  vessel  h.  This  vessel  and  the  tubes 
c  and  d  are  filled  with  water,  which  may  be  slightly  coloured  to 
facilitate  the  reading. 

2  A 


370  TECHNICAL  GAS-ANALYSIS 

The   determination   of  the   ammoniacal   nitrogen  is  made 
as  follows  :  —  The  reaction  taking  place  is 


Ten  c.c.  of  the  ammonium  salt  to  be  tested  are  introduced  into 
the  inner  vessel  a,  and  50  c.c.  of  hypobromite  solution  into  the 
outer  vessel  A.  The  rubber  stopper  is  tightly  inserted,  and  the 
vessel  placed  in  B,  which  is  filled  with  water.  Tap  /"is  loosened 
slightly  ;  water  is  forced  into  pipes  c  and  d  by  squeezing  the 
rubber  ball  i  and  opening  tap  gt  and  then  run  off  through  g  down 
to  the  zero  mark  of  the  burette  c.  After  about  ten  minutes 
the  tap/,  which  is  slightly  greased,  is  inserted  tightly,  and  set 
so  that  A  is  in  communication  with  c.  If  after  an  interval  of 
five  minutes  the  liquid  in  c  has  risen,  tap  f  is  again  loosened, 
reinserted  tightly,  and  the  apparatus  allowed  to  stand  for  five 
minutes.  If  now  the  liquid  has  remained  at  the  zero  mark, 
the  temperature  of  A  has  become  equal  to  that  of  the  water 
in  B,  and  no  more  carbon  dioxide  (from  the  air  enclosed  in  the 
apparatus)  is  absorbed  by  the  hypobromite  solution. 

Now  30  to  40  c.c.  of  this  are  withdrawn  from  the  burette 
by  opening  tap  g  ;  A  is  taken  out  of  B  and  tilted  so  that  a 
little  of  the  ammonium  salt  solution  contained  in  a  flows  into 
the  hypobromite  solution,  with  which  it  is  mixed  by  gentle 
shaking.  This  is  repeated  until  the  greater  portion  of  the 
ammoniacal  liquid  has  been  poured  out  and  decomposed. 
Tap  /  is  then  closed,  the  bottle  A  is  thoroughly  shaken,  f  is 
again  opened  to  let  the  generated  nitrogen  pass  over  into  cy 
and  this  is  repeated  until  the  water  in  c  remains  at  a  constant 
level  ;  usually  it  is  sufficient  to  shake  three  times.  A  is  then 
replaced  in  B.  After  from  15  to  20  minutes,  A  and  its  contents 
have  acquired  the  temperature  of  the  water  in  B,  and  the  gas  con- 
tained in  c  that  of  the  water  in  C.  Tap  g  is  then  opened  until 
the  water  is  at  the  same  level  in  c  and  d\  the  volume  of  the 
nitrogen  in  cy  the  temperature  of  the  water  in  C,  and  the 
barometric  pressure  are  noted. 

From  these  data  the  weight  of  the  nitrogen  can  be  calculated, 
taking  notice  that  the  reaction  as  formulated  supra  is  not  quite 
complete  (possibly  owing  to  the  formation  of  hydrazine), 
according  to  Raschig  (Chem.  Zeit.,  1907,  p.  926).  Dietrich  has 
published  tables  for  converting  the  observed  volumes  of  nitrogen 


AZOTOMETER 


371 


into  weights,  allowing  for  that  incompleteness  of  the  reaction. 
These  tables  are  given  in  Lunge-Keane,  pp.  128  to  130,  but  not 
repeated  here,  because,  as  shown  by  Classen  (Ausgew.  Methoden^ 
ii.  p.  501),  they  are  founded  on  an  incorrect  litre-weight  of 
nitrogen.  They  are,  moreover,  unnecessary,  since  Lunge  has 
shown  (Chem.  Ind.,  1885,  p.  165)  that  that  incompleteness  of 
reaction  can  be  correctly  compensated  by  increasing  the  values 
obtained  by  2-5  per  cent,  which  is  simply  done  by  calculating 
for  each  cubic  centimetre  of  the  nitrogen  obtained  (reduced 
to  o°  and  760  mm.) :  0-0012818  g.  N  =  o-ooi558  g.  NH3. 


FIG.  135. 

When  testing  for  urea,  which  is  decomposed   in  the  azo- 
tometer  by  the  reaction  : 

CO(NH2)2  +  3NaOBr  =  3NaBr  +  CO,  +  N,  + 2H2O, 


372  TECHNICAL  GAS-ANALYSIS 

Lunge  observed  a  minus  engagement  of  nitrogen  of  the 
amount  of  9  per  cent. ;  each  cubic  centimetre  of  nitrogen  (at  o° 
and  760  mm.)  therefore  indicates  0-002956  g.  urea. 

When  using  the  azotometer,  it  is  particularly  important 
that  the  temperature  in  the  generating  vessel  A  and  the 
measuring-tube  c  should  remain  constant  during  the  whole 
experiment.  If  vessel  A  holds  I5OC.C,  a  temperature  variation 
of  1°  causes  an  error  of  0-5  c.c.,  and  a  variation  of  2°,  an 
error  of  about  I  c.c.  Such  errors  of  course  influence  the 
results  considerably,  especially  if  only  small  quantities  of  gas 
are  liberated. 

A.  Baumann  recommends  a  simpler  form  of  azotometer  in 
which  the  measuring-tube  c  is  replaced  by  an  ordinary  pinch- 
cock  burette,  as  shown  in  Fig.  135  ;  the  manipulation  is  in  all 
respects  the  same  as  that  described  above.  If  many  analyses 
have  to  be  made,  it  is  well  to  employ  two  or  three  such 
simplified  azotometers,  so  as  to  save  time  for  the  cooling  after 
each  operation. 


THE  NITROMETER. 

This  name  was  given  by  Lunge1  to  the  apparatus  devised  by 
him  for  the  determination  of  nitrogen  acids  by  means  of  mercury 
and  sulphuric  acid.  This  reaction  had  been  indicated  in  1847 
by  Walter  Crum,  for  the  analysis  of  nitrates  and  of  gun-cotton  ; 
by  Frankland  and  Armstrong  in  1868,  for  the  determination  of 
nitrates  in  water;  and  by  Davis  in  1878,  for  the  valuation  of 
nitrous  vitriol ;  but  it  was  rather  difficult  and  troublesome  to 
carry  out,  which  restricted  its  applicability.  The  construction 
of  Lunge's  nitrometer,  however,  rendered  that  reaction  to  be 
easily  applied,  and  has  been  the  means  of  bringing  it  into 
general  use. 

If  nitric  acid  or  solutions  containing  a  nitrate  or  nitrite,  or 
nitroso-sulphuric  acid  ("  nitrous  vitriol "),  are  shaken  up  with 
mercury  and  strong  sulphuric  acid,  all  the  nitrogen  acids  are 
reduced  to  nitric  oxide,  which  is  measured,  and  from  the  volume 
of  which  the  weight  of  the  compound  tested  for  is  calculated. 

1  Ber.,  1878,  p.  174  ;  1895,  pp.  1878  and  2030  ;  1888,  p.  376,  and  in  many 
other  publications. 


NITROMETER  373 

First  an  unstable  substance  of  blue  colour  makes  its  appearance, 
which  was  first  observed  by  Lunge,  and  later  on  examined  by 
Sabatier  (Bui.  Soc.  Chem.,  1897,  p.  782),  Trautz  (Z.  physik. 
Chern.^  1903,  p.  601),  Raschig  (Z.  angew.  Chem.y  1905,  p.  1303), 
Lunge  and  Berl  (ibid.,  1906,  p.  807).  On  the  strength  of  these 
investigations  the  reaction  in  the  case  of  nitric  acid  can  be 
formulated  as  follows  :  — 


(1)  2HNOs  +  2Hg2  +  4H2SO4  -  2Hg,SO4  +  4H2O  +  2SO5NH(nitroso- 

sulphuric  acid). 

(2)  2SO.-NH  +  Hg2-f-H2SO4  =  Hg.2SO4  +  2SO5NH2(nitrosi-sulphonic 

acid,  blue  compound). 

(3)  2S05NH2  *  2H2S04  +  2NO. 

In  the  method  as  orginally  devised,  and  frequently  carried 
out  up  to  this  day,  the  mercury,  which  serves  as  confining  liquid, 
itself  takes  part  in  the  reaction.  It  has,  however,  been  found 
that  the  nitrometer  serves  very  well  for  a  variety  of  other  cases, 
in  which  the  gas  in  question  is  given  off  without  the  co-opera- 
tion of  mercury,  and  is  only  measured  over  this.  Both  for 
these  purposes,  but  also  for  the  original  reaction  of  Crum, 
Lunge  later  on  effected  the  liberation  of  the  gas  in  a  separate 
vessel,  and  measured  the  gas  over  dry  mercury.  Later  on 
Lunge  developed  from  the  nitrometer  his  "  Gas-volumeter," 
which  has  been  already  described  sufird,  pp.  21  et  seq. 

The  widely  extended  applicability  of  the  nitrometer  is  mainly 
due  to  the  following  reasons:  —  In  the  first  place,  most  gases, 
even  those  which  are  soluble  to  a  considerable  extent  in  water, 
can  by  its  means  be  measured  over  mercury  without  the  use 
of  a  mercury  trough,  which  previously  was  always  necessary  for 
this  purpose.  The  apparatus  is  simple,  requires  but  little 
mercury,  and  is  easy  to  manipulate  and  to  shake.  Secondly, 
it  is  equally  suitable  for  those  cases  in  which  the  gas  is  evolved 
and  measured  in  a  pure  state,  or  for  those  in  which  it  is 
liberated  in  a  separate  vessel  and  the  displaced  air  measured. 
It  can  also  be  used  for  ordinary  gas-analysis,  and  for 
determinations  in  which  a  gas,  generated  from  a  solid  or 
liquid  substance,  has  to  be  separated  from  other  gases 
as  in  the  determination  of  carbon  dioxide  by  Lunge  and 
Marchlewski's  method,  etc. 


374 


TECHNICAL  GAS-ANALYSIS 


Bockmann  (3rd  ed.,  i.  p.  63),  in  describing  the  nitrometer, 
says : — 

"Lunge's   nitrometer,   in    its   various   modifications,   is    an 
exceptionally  valuable  apparatus,  and  is  therefore  very  largely 

used  for  technical  work.  There 
is  scarcely  another  apparatus  for 
technical  analysis  which  has  so 
many  practical  applications,  and 
is  at  the  same  time  so  easily 
handled.  Those  of  its  applica- 
tions which  have  been  published 
are  numerous  ;  those  which  are 
unpublished,  and  which  are 
carried  on  in  every  technical 
laboratory,  are  certainly  still 
more  numerous." 

The  nitrometer  is  shown  in 
Fig.  136  in  its  original  form, 
as  still  used  in  most  cases  for 
the  analysis  of  nitrous  vitriol  in 
the  sulphuric  acid  industry,  and 
for  many  other  purposes.  Tube 
A  has  a  capacity  of  50  c.c. ; 
it  is  drawn  out  at  the  bottom 
and  graduated  in  i/io  c.c.  The 
graduation  starts  immediately 
below  the  three-way  tap  which 
terminates  the  tube  at  the  top. 
This  tube  may  either  have  a 
vertical  and  an  axial  passage, 
as  in  Winkler's  or  Bunte's  gas- 
burettes,  or  it  may  be  a  Greiner 
and  Friedrichs  tap  with  two 
oblique  passages,  as  shown  in 
its  three  positions  in  Fig.  137 
A,  B,  C.  The  latter  form  closes 

more  tightly,  and  is  more  easily  manipulated,  than  the  former, 
and  is  therefore  usually  attached  to  the  newer  forms  of 
apparatus.  Above  the  tap,  a  beaker-shaped  funnel  and  a 
side-tube,  d,  are  placed.  In  position  A  the  measuring-tube 


FIG.  136. 


NITROMETER 


375 


communicates  with  d\  in  position  B,  with  the  beaker  ;  in  position 
C  the  tap  is  closed. 

The  measuring-tube  A,  Fig.  136,  is  connected  by  thick- 
walled  rubber  tubing  with  the  level-tube  B.  The  latter  is  a 
simple  cylindrical  glass  tube  of  the  same  diameter  as  A,  and 
drawn  out  at  the  bottom  for  attaching  the  rubber  tubing.  Both 
A  and  B  are  held  by  clamps,  in  which  they  can  be  moved. 

To  use  the  apparatus,  for  instance  for  the  assay  of  nitrous 
vitriol,  tube  B  (Fig.  136)  is  placed  so  that  its  lower  end  is 
somewhat  higher  than  the  tap  on  A,  and  mercury  is  poured  in 
through  B,  the  tap  on  A  being  open,  until  the  mercury  enters 
the  beaker  on  A ;  as  this  takes  place  from  below,  no  air-bubbles 
are  formed  on  the  sides  of  the  tube.  The  tap  is  then  closed, 


FIG.  137. 

the  mercury  in  the  beaker-funnel  allowed  to  flow  out  through 
the  side  passage  of  the  tap,  tube  B  lowered,  and  the  tap  closed. 
The  nitrous  vitriol  is  then  run  into  the  funnel  from  a  I  c.c. 
pipette,  divided  into  y^  c.c. ;  in  the  case  of  very  strong  nitrous 
vitriol  0-5  c.c.  are  used  for  each  test,  in  that  of  weak  vitriol  2  to 
5  c.c.  The  level  -  tube  B  is  then  lowered,  the  tap  carefully 
opened,  and  the  acid  drawn  into  tube  A,  care  being  taken  that 
no  air  gets  into  this  tube.  The  funnel  is  then  rinsed  with  2  to 
3  c.c.  of  sulphuric  acid,  free  from  nitrogen  acids,  which  is 
similarly  drawn  into  tube  A,  and  the  washing  repeated  with 
another  I  to  3  c.c.  of  sulphuric  acid.  The  reaction  is  then 
started  by  removing  A  from  the  clamp,  and  thoroughly  mixing 
the  acid  with  the  mercury,  by  repeatedly  holding  the  tube 
almost  horizontally,  taking  care  that  no  acid  gets  into  the? 


376  TECHNICAL  GAS-ANALYSIS 

rubber  tubing,  and  then  sharply  raising  it  to  a  vertical  position. 
It  is  then  shaken  for  one  or  two  minutes,  until  no  more  gas 
is  evolved. 

The  two  tubes  are  then  placed  so  that  the  mercury  in  B  is 
as  much  higher  than  that  in  A  as  is  necessary  to  compensate 
for  the  height  of  the  acid  in  the  latter ;  I  mm.  of  mercury  is 
allowed  for  every  6J  mm.  of  acid.  After  the  temperature  has 
become  equalised,  the  pressure  is  exactly  adjusted  by  pouring  a 
little  acid  into  the  funnel  and  cautiously  opening  the  tap.  If 
the  gas  is  under  diminished  pressure  (which  is  preferably  aimed 
at  in  the  manipulation),  acid  will  flow  from  the  funnel  into  A  ; 
the  tap  is  at  once  closed  before  air  can  enter,  and  the  operation 
repeated  after  raising  tube  B  very  slightly.  If,  on  the  contrary, 
the  enclosed  gas  tends  to  force  its  way  through  the  acid,  the 
tap  is  closed,  tube  B  lowered  slightly,  and  the  tap  again  opened. 
With  a  little  care  these  manipulations  can  always  be  successfully 
carried  out.  The  volume  of  the  gas,  and  the  barometric 
pressure  and  the  temperature  are  observed  ;  the  latter  by  means 
of  a  thermometer,  the  bulb  of  which  is  placed  close  to  tube  A 
and  near  the  middle  of  the  column  of  gas. 

When  the  determination  is  finished,  tube  A  is  lowered,  so 
that  no  air  may  enter  on  opening  the  tap,  and  the  gas  is 
expelled  by  raising  tube  B.  The  acid  is  got  out,  either  by 
opening  the  side-tube  d  (Fig.  137),  or  in  the  older  form  of  the 
tap  through  the  axial  passage,  and  the  last  traces  are  removed 
by  means  of  filter  paper.  The  nitrometer  is  then  ready  for 
the  next  determination. 

To  make  sure  that  the  tap  on  tube  A  fits  tightly,  it  is 
greased  with  a  little  vaseline,  taking  care  that  none  of  this  gets 
inside  the  tap  so  as  to  come  into  contact  with  the  acid,  which 
would  lead  to  the  formation  of  very  badly  settling  froth. 

No  glass  tap  can  be  expected  to  keep  perfectly  tight  for 
prolonged  time  when  exposed  to  considerable  variation  of 
pressure.  A  tap  can,  however,  be  regarded  as  satisfactory,  if 
no  air-bubble  is  visible  at  the  top  of  the  tube  after  filling  it 
completely  with  mercury,  and  lowering  tube  B  during  an 
interval  of  two  hours.  Superior  to  the  ordinary  ground-in  glass 
caps  are  the  taps  provided  with  a  mercury  seal,  as  described  by 
Gockel  in  Z.  angew.  Chem.,  1900,  pp.  961  and  1238  (sold  by 
Alt,  Eberhard  and  Jager,  of  Ilmenau  in  Thuringia). 


NITROMETER  377 

The  volume  of  the  nitric  oxide  found  by  means  of  the 
nitrometer  is  reduced  to  o°  and  760  mm.  pressure  in  the  ordinary 
way.  Each  cubic  centimetre  of  NO  in  the  "normal"  state 
corresponds  to  1-3402  mg.  NO,  or  0-6257  mg.  N2,  or  1-6975  mg. 
N2O3,  or  2-8143  mg.  HNO3,  or  5-3331  mg.  nitric  acid  of  36°  Be\, 
or  4-5472  mg.  nitric  acid  of  40°  Be. 

The  determination  of  the  total  nitrogen  percentage  of 
nitrates  or  nitrites  soluble  in  water  is  carried  out  similarly. 
In  such  cases,  where  a  solid,  soluble  in  water,  is  analysed,  the 
weighed  substance  is  introduced  into  the  funnel  of  tube  A, 
dissolved  there  in  a  very  small  quantity  of  water,  the  solution 
drawn  into  the  tube,  the  funnel  rinsed  with  concentrated 
sulphuric  acid,  and  the  decomposition  carried  out  as  above 
described. 

The  concentration  of  the  sulphuric  acid  in  the  nitrometer 
must  be  kept  within  certain  limits  up  and  down.  Acids 
containing  more  than  97  per  cent.  H2SO4,  when  shaken  with 
mercury,  give  off  sulphur  dioxide,  and  must  therefore  not  be 
employed.  The  solubility  of  nitric  oxide  in  sulphuric  acid 
increases  with  the  concentration  of  the  latter.  Acid  of  96  per 
cent.  H2SO4  dissolves  3-5  volume  per  cent.  NO ;  acid  of  90  per 
cent,  2;  of  80  per  cent.,  i-i  volume  per  cent;  that  is:  10  c.c. 
sulphuric  acid  of  96  per  cent.  H2SO4  keeps  0-35  c.c,  NO  in 
solution,  and  so  forth  (Lunge,  Ber.t  1885,  p.  1391  ;  Nernst  and 
Jellinek,  Z.  anorg.  Chem.,  1906,  xlix.  p.  219;  Tower,  ibid.,  1906, 
1.  p.  382).  Hence,  for  correct  analyses  a  correction  must  be 
made  for  the  nitric  oxide  dissolved,  which  is  not  required  for 
more  dilute  acids.  On  the  other  hand,  the  employment  of 
acids  below  75  per  cent  H2SO4  gives  rise  to  the  formation  of 
grey  mud,  consisting  of  mercury  and  mercurous  sulphate,  which 
makes  it  impossible  to  take  accurate  readings.  The  correction 
of  the  nitrometer  readings  for  the  nitric  oxide  dissolved  in  the 
liquid  is  also  treated  by  Joyce  and  La  Tourette  in  /.  Ind.  Eng. 
Chem.,  1913,  p.  1017. 

In  the  analysis  of  substances  insoluble  in  water,  but  soluble  in 
concentrated  sulphuric  acid,  more  especially  dynamites  and 
pyroxylins,  for  which  purpose  the  nitrometer  is  now  nearly 
always  used,  the  solution  in  sulphuric  acid  is  also  carried  out  in 
the  beaker-funnel.  In  this  case,  in  order  to  avoid  loss  of  nitrous 
fumes,  the  device  proposed  by  Lunge  (Chem.  Ind.,  1886,  p.  274), 


378 


TECHNICAL  GAS-ANALYSIS 


as  shown  in  Fig.  138,  is  used.  The  beaker- funnel  of  the  nitro- 
meter is  closed  by  a  rubber  stopper,  provided  with  an  g-tube, 
ending  above  in  a  small  funnel.  The  substance  is  placed  in  the 
beaker,  and  concentrated  sulphuric  acid  introduced  through  the 
small  funnel.  The  S-shaped  bend  of  this  tube  remains  full  of 
sulphuric  acid,  which  prevents  the  escape 
of  nitrous  fumes,  and  which  flows  into  the 
beaker,  when  the  acid  in  the  latter  is 
drawn  into  the  measuring-tube  A. 

It  is  immaterial  whether  in  the  dissolv- 
ing operation  an  insoluble  powder,  such  as 
kieselguhr  in  the  case  of  dynamite,  or 
some  undissolved  saltpetre,  etc.,  remains 
behind,  as  this  is  sucked  into  the  meas- 
uring-tube with  the  liquid  ;  in  the  analysis 
of  pyroxylin  it  is,  however,  better  to  wait 
till  it  has  completely  dissolved  in  the 
beaker-funnel ;  when  this  is  the  case,  the 
test  is  finished  at  once,  since  on  standing 
too  long  time  too  high  values  are  found.1 

Nitrates  and  esters  of  nitric  acid^  such 
as  nitroglycerine  and  nitrocellulose,  can  be  analysed  in  the 
nitrometer  shown  in  Fig.  136,  but  a  high  degree  of  accuracy 
is  not  obtainable  therewith,  since  no  more  than  40  c.c.  of  gas 
can  be  measured  therein.  But  an  accuracy  of  o-i  per  cent., 
which  is  not  surpassed  by  that  of  any  other  method,  can  be 
attained  by  means  of  the  "  nitrometer  for  saltpetre,"  shown 
in  Fig.  139.  In  this  a  larger  space  for  gas  is  provided  without 
making  the  apparatus  inconveniently  long,  by  means  of  a  bulb 
of  nearly  100  c.c.  capacity,  below  which  the  graduations  extend 
from  100  to  130  c.c. 

In  Fig.  140  a  nitrometer  is  shown  which  may  be  used  for 
determinations,  both  when  a  large  and  when  a  small  volume  of 
gas  is  evolved.  As  it  cannot  be  made  so  short  as  the  forms 
shown  in  Figs.  136  and  139,  it  is  not  so  suitable  for  shaking, 


FIG.  138. 


1  Newfield  and  Marx  (/.  Amer.  Chem.  Soc.,  1906,  p.  877)  found  too  low 
values  when  nitrometrically  testing  explosives  containing  paraffin,  camphor, 
resins  or  vaseline,  and  too  high  results  with  those  containing"  sulphur  or 
carbonates. 


NITROMETER 


379 


de- 


but  it   is  well   adapted    for   use   in   conjunction   with   a 
composition  bottle  "  or  as  a  "  gas- volumeter  "  (see  below). 

Modified  forms  of  the  nitrometer  have  been  described  by 
Hempel  (Z.  anal.  Chem.,  1881,  p.  82),  Horn  (Z.  angew.  Chem., 
1892,  pp.  200,  358),  Pitmann  (/.  Sac.  Chem.  Ind.,  1900,  p.  983), 
Dennis  (his  Gas- Analysis,  1913,  p.  393). 


ofe 


5(  -*• 


130 


ISO 


FIG.  139. 


FIG.  140. 


FIG.  141. 


Sometimes  in  nitrometric  analyses  a  somewhat  considerable 
proportion  of  substances  insoluble  in  sulphuric  acid  are  secreted 
which  stop  up  the  tap.  For  such  cases  the  nitrometer  of 
Lubarsck,  shown  in  Fig.  143,  has  been  found  useful.  The  gas- 
measuring  tube  in  this  apparatus  is  at  the  top  bent  sideways 
in  an  angle  of  120°  for  a  length  of  5  cm.  Immediately  above 
the  bulb  is  a  zero  mark,  and  the  division  is  carried  down  nearly 
to  the  tap  closing  the  tube  at  the  bottom.  Into  the  upper 
lateral  tube  a  bent  glass  tube,  the  "receiver"  10  cm.  long, 
12  mm.  wide,  is  tightly  ground  in,  The  other  end  of  the 


380  TECHNICAL  GAS-ANALYSIS 

receiver  is  closed ;  at  the  outer  side  of  the  bend  a  funnel  is 
fused  on,  which  is  closed  at  the  bottom  by  a  tap,  at  the  top  by 
a  glass  stopper.  The  level-tube  at  its  bottom  is  fitted  with  a 
branch,  closed  by  a  rubber  tube  and  pinchcock,  for  running  off 
the  mercury.  Both  the  measuring-tube  and  the  receiver  must 
be  well  dried  before  every  test ;  the  ground  joints  and  the  glass 
tap  must  be  lubricated  with  concentrated  sulphuric  acid. 

The  weighed,  finely-powdered  example  is  introduced  into 
the  closed  part  of  the  receiver,  and  this,  the  funnel-tap  being 
opened,  .is  put  on  to  the  measuring-tube,  in  which  the  mercury 
should  stand  at  the  zero  mark.  The  funnel-tap  is  now  closed, 
and  the  requisite  quantity  of  sulphuric  acid  is  poured  into  the 
funnel.  Now  the  bottom  tap  of  the  measuring-tube  is  opened, 
a  minus  pressure  is  produced  by  running  some  mercury  out  of 
the  level-tube,  and  the  sulphuric  acid  in  the  funnel  is  sucked 
into  the  receiver,  avoiding  the  entrance  of  air.  The  tap  of  the 
funnel-tube  is  now  closed,  and  the  stopper  put  in  at  the  top. 
When  the  powder  in  the  receiver  has  been  dissolved,  which  may 
be  hastened  by  cautious  heating,  the  receiver  is  turned  180°,  and 
is  fixed  in  this  position  by  a  rubber  ring,  which  catches  a  glass 
hook  fused  on  to  the  measuring-tube.  At  first  the  receiver  is 
cautiously  shaken,  and  the  mercury  is  run  out  of  the  measuring- 
tube  at  the  rate  at  which  nitric  oxide  enters  into  it,  so  that  no 
essential  difference  of  level  is  produced  in  the  tube.  When  the 
decomposition  is  finished,  fifteen  minutes  are  allowed  to  elapse, 
and  the  volume  of  the  nitric  oxide  is  read,  after  causing  the  liquid 
in  the  two  tubes  to  assume  the  level  position,  keeping  the  mercury 
in  the  level-tube  higher  than  that  in  the  measuring-tube,  by 
one-seventh  of  the  depth  of  the  layer  of  sulphuric  acid,  standing 
above  the  mercury  in  the  latter  (cf.  supra,  p.  376).  The  volume 
of  the  receiver  up  to  the  zero  mark  of  the  measuring-tube  must 
be  known  (it  is  marked  on  the  receiver)  and  allowed  for.  Since 
the  oxygen  of  the  air  present  in  the  receiver  before  the  experi- 
ment has  been  consumed  by  being  transferred  to  the  mercury, 
the  cubic  centimetres  of  the  receiver-volume  are  multiplied  by 
0-209,  and  the  product  added  to  the  cubic  centimetres  of  NO 
read  off.  To  allow  for  the  absorption  of  NO  in  the  concentrated 
sulphuric  acid,  0-035  c.c.  per  each  cubic  centimetre  of  acid  is 
added,  and  the  result  of  the  test  calculated  in  the  same  way  as 
for  Lunge's  nitrometer  (p.  377). 


NITROMETER  381 

Lunge  (Chem.  Ind.,  1886,  p.  273)  points  out  that  this  method 
gives  wrong  results,  if  the  substance  tested  contains  carbonates 
or  other  substances  yielding  carbon  dioxide. 

Nitrometer  provided  with  a  Separate  Decomposing-bottle. — 
When  compounds  of  nitric  or  nitrous  acid  are  decomposed  by 
shaking  in  the  measuring  -  tube  itself  with  mercury  and 
sulphuric  acid,  a  layer  of  sulphuric  acid  finally  remains  between 
the  gas  and  the  mercury,  which  has  to  be  allowed  for  in  adjust- 
ing the  pressure  for  the  final  measurement,  as  stated  above 
(p.  376).  This  as  a  rule  causes  no  special  difficulty,  but  when 
considerable  quantities  of  substance  are  decomposed,  much 
frothing  sometimes  occurs ;  on  dilution  with  water,  which  is 
unavoidable  in  some  cases,  mercurous  sulphate  is  precipitated, 
and  in  the  analysis  of  dynamite  the  kieselguhr  floats  on  the 
top  of  the  acid,  etc.  These  factors  make  the  final  adjustment 
and  measurement  uncertain  and  inexact.  In  such  cases,  for 
instance  in  the  analysis  of  saltpetre  and  of  explosives,  it  is 
therefore  advisable  to  use  a  separate  decomposition  vessel, 
with  an  attached  pressure-tube,  as  in  the  gas-volumeter.  The 
gas  is  then  always  measured  over  a  sharp  mercurial  meniscus, 
and  its  volume  can  be  read  with  the  greatest  accuracy.  This 
apparatus  has  been  already  shown,  in  connection  with  the 
gas-volumeter,  supra,  p.  23,  Fig.  16,  where  the  vessel  E  serves 
for  decomposing  the  nitrous  vitriol,  etc.,  whereupon  the  nitric 
oxide  generated  is  driven  over  into  the  burette  A,  by  raising 
the  level-tube  F  and  lowering  the  level-tube  C. 

The  following  Figs.  142  and  143  show  the  combination 
of  a  nitrometer  with  a  special  decomposition  bottle  more 
clearly. 

The  manipulation  is  then  identical  with  that  of  the 
azotometer  (supra,  p.  370).  The  substance  to  be  decomposed 
is  put  in  the  outer  annular  space,  and  the  decomposing  agent 
in  the  inner  vessel,  which  is  fused  on  to  the  bottom  of  the 
bottle.  After  replacing  the  stopper,  the  bottle  is  connected 
with  the  tap  o  of  the  nitrometer ;  the  measuring-tube  A  of 
which  has  been  completely  fillled  with  mercury ;  the  stopper 
of  the  bottle  is  again  loosened,  to  make  sure  that  there  is  no 
excess  of  pressure  in  the  decomposition  bottle,  and  the  latter 
tilted,  so  that  the  liquid  in  the  inner  vessel  flows  into  the 
surrounding  space.  In  doing  this,  care  must  be  taken  that 


382  TECHNICAL  GAS-ANALYSIS 

the  bottle  is  not  warmed  by  the  hand  of  the  operator,  and 
this  applies  also  to  the  subsequent  shaking,  to  promote  the 
disengagement  of  the  gas;  it  is  safest,  especially  if  heat  is 
evolved  by  the  reaction,  as  in  decompositions  by  the  sodium 
hypobromite  method,  to  place  the  decomposition  bottle  up  to 
the  neck  in  a  beaker  filled  with  water,  before  and  after  the 
reaction.  As  the  mercury  in  the  measuring-tube  A  is  depressed 
by  the  evolved  gas,  the  level-tube  C  is  lowered  accordingly, 
to  prevent  the  pressure  from  becoming  too  high ;  it  is  some- 
times advisable  to  lower  the  level-tube  considerably  towards 
the  end  of  the  reaction,  in  order  to  facilitate  the  removal  of 
the  gas.  After  the  original  temperature  has  been  attained, 
the  mercury  is  brought  to  the  same  level  in  both  tubes,  and 


FIG.  142. 

the  volume  of  the  gas  read,  together  with  the  temperature  and 
barometric  pressure,  as  described  on  p.  277. 

In  reducing  to  760  mm.  pressure,  it  must  be  borne  in  mind 
that,  whilst  in  the  nitrometric  operations  properly  so  called,  as 
in  testing  nitrous  vitriol,  nitrates,  etc.,  the  nitric  oxide  evolved 
is  dry,  the  gas  as  evolved  from  dilute  solutions  is  moist,  and 
the  tension  of  the  aqueous  vapour  may  be  in  these  cases 
considered  to  be  equal  to  that  of  pure  water  of  the  same 
temperature. 

The  reduction  of  the  volume  of  gas  to  the  normal  volume  (at 
o°  and  760  mm.)  is  most  easily  done  by  the  tables  calculated 
by  Lunge,  and  reprinted  in  Lunge-Keane's  Technical  Methods 
of  Chemical  Analysis,  vol.  L,  Nos.  vi.  to  vii?.,  pp.  921  et  seq. ;  and 


REDUCTION  TO  NORMAL  VOLUME 


383 


in  Lunge's  Technical  Chemist's  Handbook,  table  No.  xx.  The 
calculation  can  also  be  performed  by  reversing  the  formula 
given  on  p.  24. 

The   easiest  way  of  performing  that    reduction  is  that  of 


FIG.  143. 

employing  an  apparatus  for  the  mechanical  reduction  of  the 
volume  of  gases  to  the  normal  state,  without  observing  the 
thermometer  and  barometer,  as  described  supra,  pp.  19  et  seq., 
particularly  by  \^^,  gas-volumeter  described  on  pp.  21  et  seq.  This 


384  TECHNICAL  GAS-ANALYSiS 

applies  also  to  the  apparatus  shown  in  Fig.  142,  where  the 
bulb-tube  B  serves  for  the  mechanical  reduction  just  mentioned. 

Lunge's  Technical  Chemist's  Handbook  (p.  17)  contains  a  table 
for  converting  the  cubic  centimetres  read  off  in  gas- volumetric 
analysis  into  milligrammes  of  the  substance  required  ;  also  Lunge- 
Keane,  vol.  i.  p.  146). 

Borchers  (Ger.  P.  259044)  describes  a  compensating  arrange- 
ment for  gas-volumetric  analysis  (Chem.  Zeit.  Rep,,  1913,  p.  257). 

Applications. — The  nitrometer  or  gas-volumeter,  combined 
with  a  "  decomposition  bottle,"  has  found  very  numerous 
applications,  many  of  which  have  been  described  by  Lunge 
(Chem.  Ind.,  1885,  pp.  161  et  seq.),  such  as  the  estimation  of 
carbon  dioxide  (preferably  by  the  method  of  Lunge  and 
Marchlewski),  of  nitrogen  in  ammonium  salts  by  the  hypo- 
bromite  method ;  the  same  in  urea  and  in  diazo-compounds ; 
the  control  of  the  strength  of  acids  by  liberation  of  carbon 
dioxide  from  carbonates,  the  valuation  of  zinc  dust  by  the 
hydrogen  evolved ;  altogether  in  most  cases  where  a  gas 
insoluble  in  the  decomposing  liquid,  and  not  acting  upon 
mercury  is  given  off,  by  the  measurement  of  which  the  decom- 
posed constituent  can  be  estimated. 

Particularly  numerous  are  the  uses  for  the  methods  in 
which  hydrogen  peroxide  is  used  for  decomposing  substances, 
by  giving  up  its  hydrogen  to  combine  with  the  oxygen  of 
those  substances,  and  liberating  the  whole  of  its  own  oxygen : 

XO  +  H2O2  =  X  +  H2O  +  O2. 

This  elegant  and  rapidly  executed  method  is,  for  instance,  used 
for  testing  hydrogen  peroxide  itself,  potassium  permanganate 
solution,  bleaching-powder,  manganese  dioxide,  potassium 
ferricyanide,  lead  peroxide,  iodine  solution,  chromates  (Baumann, 
Z.  angew.  Chem.,  1891,  pp.  135,  198,  339,  392),  nitrous  acid 
(Riegler,  Z.  anal.  Chem.,  1897,  p.  665). 

We  must  leave  the  special  description  of  these  methods, 
which  do  not  belong  to  gas-analysis,  to  the  general  treatises  on 
general  and  technical  analysis. 

The  nitrometer  can  also  be  used  as  an  absorptiometer 
(Lunge,  loc.  cit.)  for  most  gas-analytical  work  (ibid.} ;  for  the 
collection  and  analysis  of  gases  dissolved  in  water  (ibid.,  and 


ARRANGEMENT  OF  LABORATORY  385 

Z.  anal.  Chem.,  1886,  p.  309)  ;  for  the  determination  cf  vapour 
densities  (Lunge  and  Neuberg,  Ber.,  1891,  p.  729). 

A  modification  of  the  Lunge  gas-volumeter,  in  which  all 
the  connections  are  made  of  glass,  has  been  described  by 
Gruskiewicz  (Z.  anal.  Chem.,  1904,  p.  85). 

Special  forms  of  the  Gas-volumeter  have  been  designed  by 
Lunge  (Ber.  1890,  p.  446)  for  the  determination  of  nitrogen 
in  elementary  organic  analysis,  and  by  Lunge  and  Neuberg 
(ibid.,  1891,  p.  729)  for  the  determination  of  vapour  densities. 

Lunge  (Z.  angew.  Ghent.,  1892,  p.  578)  has  devised  a  very 
convenient  mechanical  stand  for  the  manipulation  of  the  gas- 
volumeter  (shown  in  Lunge-Keane's  book,  vol.  i.  p.  154),  which 
is  supplied  by  C.  Desaga,  Heidelberg,  by  the  name  of 
"  Universal  Gas-volumeter." 

For  the  determination  of  carbon  dioxide  in  carbonates, 
special  forms  of  this  instrument  are  described  by  Lunge  and 
Marchlewski  (Z.  angew.  Chem.,  1891,  pp.  229  and  412  ;  1893, 
P-  395  J  J-  S°c-  Chem.  Ind.,  1891,  p.  658),  and  by  Lunge  and 
Rittener  (Z.  angew.  Chem.,  1906,  p.  1849);  f°r  tne  estimation 
of  carbon  in  iron  and  steel,  and  of  carbon  dioxide  in  aqueous 
solutions  by  Lunge  and  Marchlewski  (Stahl  u.  Risen.,  1891, 
p.  666;  1893,  p.  655;  1894,  p.  624;  Z.  angew.  Chem.,  1891, 
p.  412).  These  are  described  in  Lunge-Keane's  Technical 
Methods,  vol.  i.  pp.  149  et  seq. 


ARRANGEMENT  AND  FITTINGS  OF  A  LABORATORY 
FOR  GAS-ANALYSIS 

A  person  who  has  to  carry  out  gas-analysis  for  technical 
purposes  has  in  many  cases  to  work  in  anything  but  a 
properly  fitted-up  laboratory.  He  may  be  compelled,  not 
merely  to  take  samples  of  gases  in  the  most  various  places — 
at  furnaces,  flues  and  chimneys,  in  open  yards,  in  the  field, 
or  below  ground — but  he  must  sometimes  perform  the  analysis 
in  the  same  places.  Evidently  under  such  unfavourable  circum- 
stances  the  accuracy  of  the  results  may  be  seriously  impaired, 
but  this  cannot  be  avoided. 

It  is  different  when  the  analyses  are  made  in  a  real 
laboratory.  Here  all  arrangements  can  and  must  be  provided 

2  B 


386  TECHNICAL  GAS-ANALYSIS 

which  make  it  possible  to  work  quickly  and  conveniently  as 
well  as  accurately. 

The  laboratory  ought  to  be  a  room  exposed  as  little  as 
possible  to  variations  of  temperature.  The  windows  should 
give  a  good  light,  but  should,  if  possible,  be  turned  towards 
the  north.  The  heating  apparatus  for  use  during  the  cold 
season  should  be  arranged  so  that  the  whole  room  is  as  nearly 
as  possible  at  the  same  temperature.  The  apparatus,  reagents, 
and  the  water  used  should  be  kept  in  the  laboratory  itself,  so 
as  to  be  at  the  same  temperature. 


ATOMIC  WEIGHTS 


387 


APPENDIX 

I.  Atomic  W eights  >  fixed  by  the  International  Committee  for  1914. 


Aluminium  . 

Al 

27-1 

Neodymium           . 

Nd 

144-3 

Antimony   . 

Sb 

120-2 

Neon    .        .        . 

Ne 

20-2 

Argon 

A 

39-88 

Nickel. 

Ni 

58-68 

Arsenic 

As 

74-96 

Niton    (radium   emana 

Barium 

Ba 

137-37 

tion)  . 

Nt 

222-4 

Bismuth 

Bi 

208-0 

Nitrogen 

N 

I4-OI 

Boron 

B 

II-O 

Osmium 

Os 

190-9 

Bromine 

Br 

79-92 

Oxygen 

0 

1  6-00 

Cadmium    . 

Cd 

112-40 

Palladium     . 

Pd 

106-7 

Caesium 

Cs 

132-81 

Phosphorus  . 

P 

31.04 

Calcium 

Ca 

40-07 

Platinum 

Pt 

195-2 

Carbon 

C 

12-00 

Potassium     . 

K 

39.10 

Cerium 

Ce 

I40-25 

Praseodymium 

Pr 

140-6 

Chlorine 

Cl 

35-46 

Radium 

Ra 

226-4 

Chromium  . 

Cr 

52-0 

Rhodium 

Rh 

102-9 

Cobalt 

Co 

58-97 

R  ubidium 

Rb 

85-45 

Columbium  (Nio  ium 

Cb 

93-5 

Ruthenium  . 

Ru 

Copper 

Cu 

63-57 

Samarium 

Sa 

150.4 

Dysprosium 

Dy 

162-5 

Scandium 

Sc 

44-1 

Erbium 

Er 

i67-7 

Selenium 

Se 

79-2 

Europium    . 

Eu 

152-0 

Silicon  . 

Si 

28-3 

Fluorine 

F 

19-0 

Silver    . 

Ag 

107-88 

Gadolinium 

Gd 

157-3 

Sodium 

Na 

23-00 

Gallium 

Ga 

69-9 

Strontium 

Sr 

87-63 

Germanium 

Ge 

72-5 

Sulphur 

S 

32-07 

Glucinum    . 

Gl 

9-1 

Tantalum 

T 

181-5 

Gold  . 

Au 

197-2 

Tellurium     . 

Te 

127-5 

Helium 

He 

3-99 

Terbium 

Tb 

159-2 

Holmium    . 

Ho 

I63-5 

Thallium 

Tl 

204-0 

Hydrogen  « 

H 

1-008 

Thorium 

Th 

232-4 

Indium 

In 

114-8 

Thulium 

Tu 

168-5 

Iodine 

I 

126-92 

Tin       ... 

Sn 

119-0 

Iridium 

Ir 

I93-I 

Titanium 

Ti 

48.1 

Iron    . 

Fe 

55-84 

Tungsten 

W 

184-0 

Krypton 

Kr 

82-92 

Uranium 

U 

238-5 

Lanthanum 

La 

139-0 

Vanadium     . 

V 

51-0 

Lead  . 

Pb 

207-10 

Xenon  . 

Xe 

130-2 

Lithium 

Li 

6-94 

Ytterbium      (Neoytter 

Lutecium    . 

Lu 

174.0 

bium) 

Yb 

172-0 

Magnesium 

Mg 

Yttrium 

Yt 

89-0 

Manganese. 

Mn 

54-93 

Zinc      . 

Zn 

65-37 

Mercury 
Molybdenum 

Hg 
Mo 

200.6 
96-0 

Zirconium     . 

Zr 

90-6 

388 


TECHNICAL  GAS-ANALYSIS 


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STANDARD  SOLUTIONS 


391 


V.  Standard  Solutions  for  Technical  Gas- Analysis. 


1  vol.  gag  at  7*0  mm. 
and  0°,  in  the  dry 

state. 

Formula. 

Indicated  by  1  vol.  of  a  solution 
containing  per  litre. 

Grams. 

Ammonia 

NH3 

2-1807  Sulphuric  acid 

H2S04 

9t                               •                • 

•  t 

2-5075  Potassium  hydroxide    . 

KOH 

Carbon  monoxide    . 

CO 

5-6296  Oxalic  acid,  crystal. 

C2H2O4,  2H2O 

M                                  * 

140943  Barium     hydroxide, 

crystal 

Ba(OH)2,  8H2O 

Carbon  dioxide 

C02 

5-6296  Oxalic  acid,  crystal. 

C2H204,  2H20 

>»             '    • 

M 

14-0943  Barium     hydroxide, 

crystal 

Ba(OH)2,  8H2O 

Chlorine 

Cl 

4-4216  Arsenic    trioxide,     dis- 

solved     in      sodium 

bicarbonate        * 

As2O3 

»i               •        • 

1) 

n-3353  Iodine,     dissolved      in 

potassium  iodide 

I 

Hydrogen  chloride  . 

HC1 

4-8215  Silver,      dissolved      in 

nitric  acid 

Ag 

»5                                    • 

3-4028  Ammonium     sulphocy- 

anide 

CNS,  NH4 

M                                 • 

2-5075  Potassium  hydroxide    . 

KOH 

Methane 

CH4 

5-6296  Oxalic  acid,  crystal. 

C2H204,  2H20 

140943  Barium    hydroxide, 

»» 

n 

crystal 

Ba(OH)2,  8H2O 

Nitrogen  trioxide    . 

N203 

5-6230  Potassium   permangan- 

ate   . 

KMnO4 

Nitric  oxide    . 

NO 

4-2406  Potassium    permangan- 

ate   . 

|| 

Sulphur  dioxide 

SO2 

11  "33  5  3  Iodine,     dissolved     in 

potassium  iodide 

I 

»>                 • 

11 

50166  Potassium  hydroxide    . 

KOH 

ADDENDA 


Page  14.  A  gas-sampling  apparatus  has  been  described  by 
A.  E.  Carr  in  his  B.  P.  of  i6th  March  1912  and  Ger.  P.  270351. 

Another  by  F.  Hoffmann,  La  Roche  &  Co.,  in  Ger.  P.  272875, 
which  automatically  takes  samples  in  rotation  from  various 
places,  in  connection  with  a  measuring  and  checking  apparatus. 

Page  1 6.  Vessels  for  carrying  gas  samples.  According  to 
Murmann  (Chem.  Zentralb.,  1914,  i.  1722)  such  vessels  ought  not 
to  be  made  of  zinc,  whereby  carbon  dioxide  is  absorbed,  but 
of  sheet  brass. 

Page  no.  A  Gas-analytical  apparatus  in  which  the 
capillaries  are  fused  to  the  absorbing  vessels,  in  order  to  avoid 
india-rubber  joints,  is  described  by  Wempe  in  Z.  angew.  Chem., 
1914,  i.  271. 

Another  apparatus,  in  which  a  measured  quantity  of  a 
liquid  reagent  is  treated  with  constantly  new  quantities  of  the 
gas  to  be  examined  until  the  reagent  is  saturated,  is  described 
by  Heinemann  in  his  Ger.  P.  273726. 

Billings  (Amer.  P.  1089390)  describes  an  Orsat  apparatus  with 
a  sample-collecting  attachment  controlled  by  clockwork,  which 
regulates  automatically  the  time  during  which  the  sample  of 
gas  is  taken. 

Page  187.  The  registering  gas-balance  for  the  continuous 
indication  of  the  specific  gravity  of  gases  in  motion,  constructed 
by  Simmance  and  Abady,  and  mentioned  on  page  187,  is  very 
favourably  reported  on  by  Friedrich  Lux,  in  Gasbeleucht,,  1914, 
pages  416  et  seq. 

393  2    C 


394  ADDENDA 

Page  241.  Estimation  of  Carbon  monoxide.  Sinnatt  and 
Cramer  (Analyst,  1914,  p.  217)  recommend  the  iodine  pentoxide 
method  for  which  they  give  detailed  prescriptions. 

Moser  and  Schmid  (Z.  anal.  Cftem.,  1914,  p.  217)  convert 
the  carbon  monoxide  into  dioxide  by  passing  it  through  pre- 
cipitated mercuric  oxide,  and  estimating  the  CO2  formed  by 
absorbing  it  in  N/4  barium  hydroxide  solution  and  retitrating 
the  excess  of  the  latter. 


INDEX    OF    NAMES 


ABADY,  192 

Ab-der-Halden,  303 

Ados,  231 

Agraz,  in 

Akkumulatorenfabrik  271 

Albrecht  and  Miiller,  302 

Alkali  Inspectors,  245,  334,  341,  346 

Allgemeine    Feuerungstechnische    Gesell- 

schaft,  233,  235 
Allner,  201 
Anderson,  95,  229 
Andrews,  332 

Arndt,  ill,  112,  186,  230,  231,  235,  355 
Arnold  and  Menzel,  219 
Aron,  66 

Arzberger  and  Zulkowsky,  II 
Aston,  187 
Atkinson,  235 
Auer-Welsbach,  191 

BABB,  77 
Babbitt.  93 
Bachfeld  &  Co.,  367 
Baessler,  327 
Barnes,  19 

Earnhardt  and  Randall,  78 
Baskerville  and  Stevenson,  316 
Baudisch  and  Klinger,  318,  321 
Baumann,  121,  372,  384 
Baxter,  313 
Bayer,  327 
Beckmann,  271 
Bement,  78 
Bendemann,  81 
Berge,  285 

Berthelot,  34,  217,  286 
Berthelot  and  Gaudechon,  281 
Biehringer,  253 
Billings,  393 
395 


Binder  and  Weinland,  218 

Blair,  259 

Bockmann,  374 

Bodenstein  and  Pohl,  247 

Bodlander,  30 

Bohr  and  Bock,  31 

Bombard  and  Konig,  187 

Bone  and  Wheeler,  103,  in 

Borchers,  21,  384 

Bosshard  and  Horst,  264 

Boulton,  112,  235 

Boussingauld,  1 2 1,  123 

Boys,  201,  207 

Brach,  220 

Brady  and  Martin,  76 

Brandt,  168 

Bredig  and  Miiller  von  Berneck,  121 

British  Alkali  Makers'  Association,  339 

Brubaker,  235 

Brunck,  114,  131,  167,  242,  271,  274 

Briinnig,  329 

Bucher,  201 

Bujard,  305 

Bunsen,  10,  31,  34,  47,  52,  97,  156,  180, 

181,  211,  324 
Bunte,   58,   59,   165,   168,  169,    171,   173, 

239,  250,  288 

Bunte  and  Eitner,  359,  361,  363 
Burell,  271 
Burkhardt,  187 
Burrell,  no,  241 
Burrell  and  Seibert,  2,  in 
Butjagin,  352 

CALAFAT  y  Leon,  218 
Calvert  and  Cloe'z,  123 
Campbell  and  Parker,  281 
Cario,  70 
Caro,  284 


396 


INDEX  OF  NAMES 


Carpenter  and  Linder,  341 
Carr,  393 

Casares  and  Pina  de  Rubies,  237 
Cavendish,  217 
Centnerszwer,  122 
Chabaud,  188 
Chandler,  186 
Chevreul,  122 
Chlopin,  217 
Classen,  371 

Clayton  and  Skirrow,  307 
Collie,  128 

Colman  and  Smith,  299,  301 
Contzen,  187 
Coquillon,  267,  268,  269 
Coste  and  James,  201,  210 
Craig,  231 
Cross,  in 
Crum,  372,  373 
Gumming,  87,  95 
Cushman,  38 

Czako,     128,    178,    220,    238,    281,    288, 
356 


DAVIDSON,  in 

Davis,  338,  372 

Davy,  121 

Dejeanne,  229 

Deniges,  351 

Deniges  and  Chelle,  351 

Dennis,  15,  7°,  78,  79.  87,  93,  n6,  156, 

176,  223,  379 
Dennis  and  O'Brien,  150 
Dennis  and  Hopkins,  93,  270 
Dennis  and  McCarthy,  108,  289 
Dennis  and  O'Neill,  289,  295 
Desaga,  183 
Deville,  295,  303 
Dickert,  264 
Dietrich,  370 
Divers,  317,  320 
Doebereiner,  122 
Donau,  240 
Dosch,  187,  230,  266 
Dragerwerk,  116,  235 
Drehschmidt,  7,  21,  92,  100,  116,  127,  147, 

149, 155, 172,  260,  262,  264,  275,  276,  283, 

286,  321,328,  329 
Dulong,  176 
Dumreicher,  315 
Dupasquier,  250 


van  ECK,  219 

Eckardt,  no 

Egnell,  no 

Eiloart,  254 

Einer  Johnson,  in 

Eitner  and  Keppeler,  283 

Ellms  and  Hauser,  347 

Elster,  49,  327 

Engler  and  Wild,  219 

Erdmann,  178 

Eyer,  in 

Eynon,  III 

Evans  and  Poleck,  260 

FAHRENHEIM,  201 

Fairley,  259 

Feld,  308,  330 

Fellner,  352 

Felser,  171,  313 

Ferchland,  349 

Ferry,  324 

Fieber,  81 

Finkener,  12,  330 

Fischer,  F.,  5,  6,  66,  71,  95,  128,  149,  200, 

207,  260,  304 
Fischer,  H.,  11 
Fischer  and  Marx,  219 
Fischer  and  Ringe,  324 
Fleming-Stark,  345 
Fletcher,  189 
Fodor,  113 
Francke,  65 
Frankel,  284,  286 
Frankland  and  Armstrong,  372 
Frankland  and  Ward,  95 
Frantz,  340 
Franzen,  125,  360 
Freitag,  305 
Frenzel,  115,  125 
Fresenius,  249,  276 
Friese,  114 

Fritzsche,  115,  287,  288 
Fronsac,  303 
Fuchs,  145 

GALTHER,  285 

Ganassini,  248 

Gas  de  Paris,  Societe,  304 

Gasch,  329 

Gaskell,  Deacon  &  Co.,  342 

Gasmotorenfabrik  Deutz,  78 


INDEX  OF  NAMES 


397 


Gatehouse,  285 

Gautier,  242 

Gautier  and  Clausmann,  127,  240 

Gebhardt,  76 

von  Geldern  &  Co.,  187 

German  Acetylene  Union,  285 

Gockel,  24,  31,  33,  34,  95,  107,  229,  376 

Goldberg,  254 

Grafe,  209 

Graham,  121,  129 

Gray,  3,  8,  II,  no 

Grebel,  176 

Greiner  and  Friedrichs,  52,  59,  79,  361 

Griess,  316 

Guasco,  313 

Giilich,  183 

Gwiggner,  309 

HABER,  168,  176,  236,  277 

Haber  and  Leiser,  277 

Haber  and  Lowe,  177,  266 

Haber  and  Oechelhaiiser,  119,  286,  287, 
290 

Hahn,  81 

Haldane,  218,  242,  355 

Hale  and  Mella,  217 

Hankus,  81 

Harbeck  and  Lunge,  286,  290 

Harcourt,  Vernon,  19,  251,  255 

Harding  and  Johnson,  250 

Harger,  in,  313 

Hartley,  196 

Hartung,  III,  235 

Hasenclever,  349  % 

Hauser,  272 

Hauser  and  Herzfeld,  271 

Hawley,  248 

Hayes,  in 

Heckmann,  112,  190 

Hefner,  211 

Heinemann,  393 

Heinz,  81 

Hempel,  21,  82,  83,  86,  87,  89,  92,  93,  ico, 
114,  124,  125,  128,  129,  156,  158, 
159,  164,  172,  173,  178,  209,  238,  239, 
257,  262,  276,  315,  324,  341,  342,  379 

Hempel  and  Dennis,  289,  304 

Hempel  and  Kahl,  284 

Henrich,  17 

Henrich  and  Eichhorn,  172,  324 

Henry,  164 

Henz,  246 


Hesse,  113,  135,223,243,275 

Heymann,  323 

Hill,  93 

Hinmann,  237 

Hinman-Jenkins,  264 

Hinrichsen,  284 

Hoffmann,  La  Roche  &  Co.,  393 

Hofman,  254 

Hofsass,  183,  187 

Hohensee,  176 

Holm  and  Kutzbach,  266 

Honigmann,  58 

Horn,  379 

Horold,  164 

Horwitz,  354 

Houzeau,  219 

Hiifner,  95,  in 

Huntly,  3 

ILOSVAY,  253,  281 
Immenkotter,  2OI 
Inglis,  341 

JAEGER,  172,  173 

Jahoda,  277 

Jeller,  271 

Jenkin  and  Pye,  367 

Jenkner,  309 

Johnson,  Einer,  230 

Jones,  235 

Jorisen  and  Rutten,  301 

Joyce  and  La  Tourette,  377 

Junckers,  196,  201,  207,  209 

KALAHNE,  187 

Kalle&  Co.,  131 

Kast  and  Behrend,  250 

Kastle  and  M'Hargtie,  247 

Kaufman  &  Co.,  70 

Keiser,  148 

Reiser  and  M 'Master,  219 

Keppeler,  283,  285 

Kershaw,  114 

Kinnicutt  and  Sandford,  242 

Kjeldahl,  325 

Kleine,  in 

Klinger,  217,  318 

Knoll,  in,  187,  235 

Knop,  368 

Knorre,  129,  172,  315,  317,  321 

Knorre  and  Arendt,  118,  150,  286,  319 

Knowles,  93 


398 


INDEX  OF  NAMES 


Knuch  and  Ruppin,  17 

Koehler  and  Marqueyrol,  318 

Konig,  187,  235 

de  Koninck,  125,  217 

Korbuly,  290,  298 

Korting  Brothers,  n 

Krause,  113 

Kraushaar,  271 

Kreitling,  33 

Krell,  1 86 

Krell  u.  Schultze,  230 

Kreusler,  19,  125 

Krueger  and  Moeller,  220 

Kullgren,  247 

Kunkel  and  Fessel,  353 

Kuntz-Krause,  328 

Kiister,  299 

Kyll,  146 

LANDAU,  177,  281 

Landolt-Bb'rnstein-MeyerhofTer,  31 

Lange,  55,  223,  361 

Lange  and  Hertz,  362,  363 

Langen,  187 

Lassaigne,  124 

Laurain,  303,  304. 

Lebeau  and  Damiens,  134,  178,  279,  282, 
304 

Lechner,  220 

Le  Docte,  70 

Leeds,  121 

Lehmann,  145,  354,  355 

Leon,  218 

Leutold,  165 

Levy,  in,  169,  239,  243,271 

Lewes,  123 

Ley  bold,  321 

Lidholm,  284 

Liebig,  J.,  122,  336 

Liebig,  M.,  338 

Liese,  in 

Lindemann,  121,  211,  212,  222,  338 

Ljungh,  243,  247 

Llorenz,  282 

Lomschakow,  8r,  no 

Lovett,  338 

Lowe,  176 

Lubarsch,  128,  379 

Lubberger,  216 

Lunge,  19,  20,  21,  24,  25,  26,  28,  31,  33, 
47,-  53,  66,  71,  137,  141,  142,  146, 
188,  19',  217,  246,  314,315,  318,320, 


333,  335,  336,  338,  339.  34*,  342,  343, 

348,  352,  371,  372,  373,  374,  377,  380, 

381,  382,  383,  384,  385 
Lunge  and  Akunoff,  286 
Lunge  and  fieri,  47,  152,  156,  211,  282, 

357,  373 

Lunge  and  Cedercreutz,  150,  284 
Lunge  and  Harbeck,  4,  15 
Lunge  and  Ilosvay,  319 
Lunge-Keane,  77,  112,  151,  188,  189,  191, 

192,  193,  200,  211,  217,  221,  223,  237, 

259,    344,     352,    355,    37i,    382,    384, 

38S 

Lunge  and  Marchlewski,  29,  384,  385 
Lunge  and  Naef,  337 
Lunge  and  Neuberg,  385 
Lunge  and  Offerhaus,  350 
Lunge-Orsat,  71,  96 
Lunge  and  Rittener,  350,  385 
Lunge  and  Zeckendorf,  142,  144,  223,  243 
Liitke,  190 

Lux,  183,  186,  209,  246,  393 
Lux  and  Precht,  230 

M 'BRIDE  and  Weaver,  264 

M'Coy  and  Tashiro,  235 

Macklow,  Smith,  and  Fallen,  210 

M'Leod,  95 

Makowka,  282 

Manchot  and  Friend,  126 

Mann,  122 

Mannich,  271 

Martens,  112,  115 

Mathers  and  Lee,  103,  279 

Matzerath,  in 

Mauricheau,  284 

Mayer  and  Schmiedt,  209 

Meriam  and  Birchby,  305 

Mertens,  233,  271 

Metropolitan  Gas  Referees,  207 

Meyer,  Felix,  183,  187 

Milbauer  and  Stanek,  364 

Miller,  James,  217 

Moeller,  114 

Mohr,  177,  335 

Moir,  223 

Moissan,  284 

Moser,  320,  321 

Moser  and  Schmid,  393 

Muencke,  66 

Miiller,  237,  289 

Murmann,  393 


INDEX  OF  NAMES 


399 


Murschhauser,  368 
My  hill,  183 

NAEF,  68 

Namias,  70 

National  Physical  Laboratory,  38,  47 

Natus,  324 

Nernst  and  Jellinek,  377 

Nesmjelow,  242 

Neubaur,  313 

Neumann,  81 

Newfield  and  Marx,  378 

Nicloux,  242 

Nicolardet,  50 

Niemeyer,  264 

Normal  -  Eichungskommission        (Normal 

Standards  Commission),  34,  39 
Nourrisson,  351 
Nowicki,  127,  238 

OLDENBOURG,  183 
Olschewsky,  68 
Orsat,  66,  116,  156 
Orsat-Lunge,  71,  169 
Ost,  150,  243 
Ostwald,  37,  38 

PAAL  and  Gerun,  131 

Paal  and  Hartmann,  131 

Pagenstecher,  328 

Pal  &  Co.,  233 

Pannertz,  187 

Parr,  2io 

Peclet,  189 

Pereira,  265 

Pettenkofler,  223 

Patterson,  21,  100 

Petterson  and  Palmquist,  229 

Pfeiffer,  30,  65,  105,  116,  126,  152,  154, 
156,  163,  183,  197,  200,  2ii,  212,  213, 
215,  217,  225,  228,  230,  253,  260,  262, 
290,  293,  295,  296,  300,  302,  306, 
327,  330 

von  der  Pfordten,  125 

Philip  and  Steele,  169,  309,  313 

Phillips,  115,  265 

Philosophoff,  349 

Pictet,  Comp.  Ind.  des  Proc.,  362 

Pintsch,  55 

Pitman,  379 

Pleyer,  209 

Polek,  123 


Pollack,  282,  314,  315,  319 

Polstorff  and  Meyer,  336 

Pontag,  242,  355 

Potain  and  Drouain,  238,  240 

Preuss,  8 1 

Pring,  221 

Priestley,  215 

Primavesi,  76 

RAMSAY  and  Travers,  17,  176,  178 

Raoult,  59 

Raschig,  141,  244,  337,  339,  370,  373 

Raupp,  209 

Rayleigh,  Lord,  172,  176,  177,  277 

Reckleben  and  Lockemann,  367 

Regnault  and  Reiset,  66 

Reich,  137,  140,  141,  243,  244,  322,  323, 

335,  336,  339 

Reichsanstalt,  physico-technical,  36 
Rey,  26 
Reychler,  285 
Rhodes,  330 
Riban,  353 
Richardt,  168 
Richter,  247 
Riedinger,  49 
Riegler,  384 

Roscoe  and  Scudder,  313 
Rose,  330 
Rosen,  271 
Ross  and  Race,  251 
Rossel  and  Landriser,  285 
Rotawerke,  49,  50 

Rothmund  and  Burgstaller,  220,  221 
Rowicki,  8 1 
Rubner,  354 
Rubner  and  Renk,  114 
Riidorff,  227 
Rupp,  235 

SABATIER,  373 
Salleron,  66 
Samter,  233 
Sanders,  1 1 1 
Sandmeyer,  126 
Sarco  Fuel  Co.,  1 1 1 
Scheiber,  134 
Scheurer-Kestner,  113 
Schilling,  181,  183 
Schlatter  and  Deutsch,  233 
Schleicher  and  Schiill,  114 
Schloesjng  and  Rolland,  66 


400 


INDEX  OF  NAMES 


Schloesser,  34,  39,  45,  47 

Schlumberger,  302 

Schmid,  in,  235 

Schmidt  and  Haensch,  loi 

Schmitz-Dumont,  254 

Schonbein,  221,  317,  328 

Schb'ne,  221 

Schorer,  II 

Schorrig,  219 

Schroeder,  114,  118 

Schuhmacher,  6$ 

Schultze,  230 

Schultze  and  Koepsel,  266 

Schwartz,  York,  256 

Seger,  156,  187 

Seidell,  242 

Seidell  and  Meserve,  243 

Sieber,  348 

Siebert  and  Kiihn,  78,  172 

Siegert,  230 

Siemens  and  Halske,  ill 

Silbermann,  115 

Simmance,  Abady,  and    Wood,   ill,   187, 

209,  393 
Simon,  114 

Sinnat  and  Cramer,  242,  394. 
Smith,  210 
Smith,  R.  Angus,  142 
Societe  Roubaisienne  and  Ferrieres,  298 
Sodeau,  76,  77 
Somerville,  251,  264 
Soxhlet,  114 
Spencer,  93 
Spitta,  242 
Sprengel,  10,  II 
Stapf,  113 
Stavorinus,  289 
St  Claire  Deville,  8 
Steinbock,  233 
Stock  and  Nielsen,  32,  360 
Stocker  and  Rothenbach,  209 
Strache,  210,  233 
Strohlein  &  Co.,  76,  78 
Strong,  115 
Strype,  338 
Stuckert,  176 

TAMM,  127 
Tanda,  115 
Taplay,  no 
Teichmann,  357 
Than,  in 


Thisle  and  Deckert,  359,  360,  362 

Thomas,  95 

Thomson,  177 

Thorner,  8 1,  156,  271 

Threlfall,  187 

Tieftrunk,  49,  306 

Tiemann  and  Preusse,  17 

Tillmans,  237 

Tissandier,  113 

Tower,  377 

Trautz,  337,  373 

Travers,  128,  178 

Treadwell,  8,  15,  44,  165,  167,  237,  239, 

282,  287,  298,  349,  360,  362 
Treadwell  and  Anneler,  220 
Treadwell  and  Christie,  349,  3<o 
Treadwell  and  Stokes,  119,  286,  290 
Tucker  and  Moody,  288 

UBBELOHDE,  50 
Ubbelohde  and  de  Castro,  176 
Uehling  Instrument  Co.,  235 
Uehling  and  Steinhart,  230 
Underfeed  Stoker  Co.,  235,  236 
United  States  Bureau  of  Standards,  47 
Urban,  357 

VAIL,  171,  305 

Verbeck,  190 

Vereinigte   Fabriken    fur    Laboratoriums- 

bedarf,  230,  233 
Verschaffelt,  177 
Vogel,  121,  237,  253 
de  Voldere,  93 
Volhardt,  147,  335,  336 
Volta,  156,  283 
Votocek,  252 

WADE,  195 

Wagner,  368 

Wallis,  331 

Wanklyn  and  Cooper,  217 

Watson,  341 

Wattebled,  235 

Wempe,  16,  393 

Wencelius,  74 

Wendriner,  1 8,  271 

Wentzel,  359 

Wentzki,  367 

Werder,  358,  366 

Weyl  and  Zeitler,  122 

Weyman,  210 


INDEX  OF  NAMES  401 

White,  93  Wolff,  177 

de  Wilde,  286  Woodroffe  and  Boultbee,  1 1 1 

Wilfarth,  325  Worrell,  176,  242 

Wilhelmi,  8 1  Worstall,  118 

Willgerodt,  284  Woy,  359 

Winkler,  Clemens,    6,    8,   16,   19,   31,    52,       Wright,  249 

53,  55.  84,92,  "9,  "3,  US,  164,  165,       Wright  &  Co.,  183,  241 

176,  223,  239,  269,  270,  272,  276,  280, 

3H,338  YOKOTE,  353 

Winkler,  L.  W.,  217,  218,  223,  237,  240,       York-Schwarz,  257 

242,  252,  327  Younger,  344 
Winkler-Lunge,  8,  14 

Winkler  and  Zahn,  367  ZECKENDORF,  142 

Wislicenus,  11$,  150,  243,  352  Zeiss,  176,  177 

Witzek,  257  Zenghelis,  265 


INDEX    OF    SUBJECTS 


ABSORBENTS  for  gases,  no 

for  carbon  dioxide,  117 

for  heavy  hydrocarbons,  117 

for  oxygen,  119 

for  carbon  monoxide,  126 

for  nitrogen,  128 

for  nitric  oxide,  128 

for  hydrogen,  129 

for  unsaturated  hydrocarbons,  132 
Absorbing  apparatus,   65,   66,  71,    76,  78, 
84,  85,  86,  87,  96,  102,  106,  145,  146, 

H7 

for  solid  reagents,  85 
Absorbing  -  solutions        for      the       Orsat 

apparatus,  70 

Absorption,  estimation  of  gases  by,  116 
Absorption-coil,  145 
Absorption-pipettes,  Hempel's,  84 
Accuracy,  degree  of,  I 
Acetylene,  estimation,  118,  119,  132,  147, 

281 
Acetylene,  impurities  of  crude,  estimation, 

150,  282 
Acids,  total,  in  pyrites-kiln  gases,  etc.,  141, 

245,  246 
in  acid  fog,  245 

in  exit-gases  from  vitriol  chambers,  341 
Acid-smoke,  150 

Acoustical  methods  for  gas-analysis,  178 
Ados,  70,  231,  247 
Air,  atmospheric,  impurities,  351 
injurious  effects  of  these,  355 
Ammonia,  estimation,  325,  370 

liquefied,  analysis,  362 
Analytical    processes     employed    in    gas- 
analysis,  2 

Anemometers,  188,  189 
Aniline  vapour,  355 
402 


Apparatus   provided  wilh  absorbing  parts 
separated    from    the   measuring-tube, 

65 
Apparatus  for  gas-analysis,  50,  393 

for  rapid  and  continuous  analysis,  1 1 1 
Aqueous  vapour,  tensions,  25 
Aspirating  apparatus,  8 

by  hand  or  foot  blowers,  9 

by  steam,  9 

Sprengel  (Bunsen)  pump,  10 

water-jet  pumps,  II 

aspirating-bottles,  12 

automatic  gas-sampler,  14 
Aspirating-tubes.     See  Tubes 
Atomic  weights,  387 
Autolysator,  233,  247 
Automatic  gas-sampling  apparatus,  14 
Azotometer,  368 

BAROSCOPE,  30 

Benzene  vapour,  estimation,  108,  119,  167, 
288 

by  absorption  in  alcohol  or  paraffin  oil, 
289 

by  bromine  water,  290 

as  dinitrobenzene,  290 

by  freezing,  295 

calculation  from  the  specific  gravity,  296 

general  remarks,  298 
Board  of  Trade  unit,  191 
British  thermal  unit,  191 
Bromine,  estimation,  351 
Bromine  water  as  absorbing  agent,  119 
Bunsen  pump,  10 
Bunsen  valve,  68 
Bunte  burette,  58 

modifications,  65 
Burettes.     See  Gas-burettes 


INDEX  OF  SUBJECTS 


403 


CALCULATION  of  gas-analyses,  <)S 
Calibration  of  gas-measuring  apparatus,  33 

corrections  for  temperature,  39 

of  gas-burettes,  44 
Calorific  value  of  gases,  190,  194 

calculation  from  gas-analysis,  193 

direct  measurement,  196 
Calorimeter,  of  Junckers,  196 

modifications,  201 

of  Boys,  201 

of  Fischer,  207 

various,  209 
Carbon  dioxide,  examination,  55,  56,  57 

estimation,  69,  76,  89,  96,  107,  136,  142, 

222 

apparatus  of  Winkler,  222 

of  Hesse,  223 

of  Pfeiffer,  225 

of  Riidorf,  227 

other  apparatus,  229 

rapid  and  continuous  estimation  in  fire- 
gases,  etc.,  229 

heat-effect  meters,  231 

"Ados,"  231 

other  apparatus,  233 

"  Autolysator,"  233 

various  apparatus,  235 

detection  of  minute  quantities,  235 

various  methods,  236 
Carbon  dioxide,  liquefied,  analysis,  365 
Carbon  disulphide,  detection,  254  ;  estima- 
tion, 147,  253,  254 
Carbon  monoxide,  detection,  237 

quantitative   estimation,  64,  69,  75,  89, 
97,    109,    152,    153,    154,  167,  239, 

394 

Carbon  oxy sulphide,  256 
Carburometer,  268 
Carrying- vessels      for     gases,     14.       See 

vessels 

Cathetometer,  32 
Chlorine,  examination   for  carbon  dioxide, 

57,  348 

estimation,  136,  342 
of  minute  quantities,  344,  351 
Chlorine,  liquefied,  analysis,  365 
Chromium  protochloride  as   absorbent  for 

oxygen,  125 
Coal-gas,  analysis,  162,  178,  356 

estimation  of  carbon  dioxide  in  it,  225, 

227 
Collecting- vessels  for  gases,  14 


"  Comburimeter,"  Grebel's,  176 
Combustion,  estimation  of  gases  by,  151 

general  observations,  151 

changes  of  volume  by  it,  151 

calculating  methods,  152 

combustion  by  explosion,  155 

by  heated  platinum  or  palladium,  164 

fractional,  71,  78,  164,  169 
Combustion  of  gases,  390 

changes  of  volume,  389 
Combustion-pipette,  Hempel's,  89,  92,  93 
Compensator  for  gas-volumes,  2 1 
Compressed  gases,  357 
Confining-liquids  for  gases,  30 
Cooling;    arrangements    for    gas-sampling 

tubes,  5,  6,  7 
Coometer,  233 

Copper  as  absorbent  for  oxygen,  124 
Correction     of     volumes     for     "  normal " 

temperature  and  pressure,  2 
Cupric  oxide  for  the  combustion  of  gases, 

172,  176 
Cuprous  chloride  as  absorbent    for  carbon 

monoxide,  126 
Cyanogen,  321 

DEACON  process  gases,  342,  348 
Decomposition  flask  for  gas-volumeters,  29 
Density  of  gases,  388 
Dowson  gas,  356 
Drehschmidt's  apparatu?,  100 
Dust  in  gases,  estimation,  1 12 

ECONOMETER,  l86 

Ethane,  estimation  by  combustion,  155 

Ether  vapour,  354 

Ethylene,  estimation,  109,  119,  167,286 

Eudiometer,  52 

Exit-gases  from  vitriol  chambers,  357 

Explosion  burette,  Bunte's,  171 

Explosion  methods    for   combustion,    155, 

163,  171 

Explosion-pipette,  90,  156 
Pfeiffer's,  163 

FERROCARBONYL,  313 

Ferrous  sulphate   as   absorbent    for   nitric 

oxide,  129 
Ferrous  tartrate   as  absorbent  for  oxygen, 

125 

Filtration  of  gases,  114 
Fire-damp,   estimation   of    methane   in   it, 

161,  267 


404 


INDEX  OF  SUBJECTS 


Fire-gases,  356 
Fletcher  bellows,  333 
Fluohydric  acid,  353 
Furnace-gases,  356 

GAS-BALANCE,  registering,  393 
Gas  baroscope,  21 
Gas-burettes,  50 

Winkler's,  52 

Lange's,  55 

Honigmann's,  58 

Bunte's,  58 

modifications  of  this,  65 

Hempel's,  82 

F.  Fischer's,  95 

Gas-detector,  Philip  and  Steele's,  169 
Gas-meters,  47 
Gas-volumeter,  Lunge's,  21,  373 

manipulation,  27 

decomposition-flask  for  it,  29 
Gas-volumetric  analysis,  368 
Gay-Lussac  towers,  exit-gases,  337 
Geissler  taps,  53 
Glass  stopcocks,  15,  24,  68 
Glass  vessels  for  gases,  1 5 
Griess-Lunge  reagent,  316 
Grisou,  267 
Grisoumeter,  267 

HARGREAVES    process,    gases  evolved  in 

it,  335 

Heat,  unit  of,  191 

Heavy  hydrocarbons  in  coal-gas,  304 
Hempel's  apparatus,  82 

modifications,  93 

explosion  methods,  156 
"  Hydro"  apparatus,  187 
Hydrocarbons,  combustion  of,  91,  97 

heavy,  absorbents  for,  117 

unsaturated,  absorbents  for,  132 
Hydrofluosilicic  acid,  352 
Hydrogen,  compressed,  analysis,  367 
Hydrogen,  estimation  by  the  Lunge-Orsat 
apparatus,  71 

by  Hempel's  burette,  90 

in  F.  Fischer's  apparatus,  97 

by  Pfeiffer,  109 

absorbents  for  it,  129 

estimation  by  combustion,  152 

by  explosion,  156 

in  water-gas,  etc.,  160 

together  with  methane,  162 


Hydrogen,    by    palladium    asbestos,    167, 

169,  174 

qualitative  tests,  255 

quantitative  estimation,  266 

mixtures  with  ethane,  propane,  etc.,  279 
Hydrogen  arsenide,  353 
Hydrogen  chloride,  136,  145,  333,  338 
Hydrogen  cyanide,  328,  338 
Hydrogen  peroxide,  221 
Hydrogen  phosphide,  150,  352 
Hydrogen  pipette,  Hempel's,  158,  159 
Hydrogen  sulphide,  estimation,  147 

in  crude  acetylene,  150 

ILLUMINATING  gas.    See  Coal-gas 
Illuminating  power  of  gases,  210 
India-rubber  blowers  for  aspirating  gases, 
Inflammable  gases  in  the  air,  309 
Interferometer,  177,  277 
lodic     acid      as     absorbent     for      carbon 
monoxide,  127 

LABORATORY  for  gas-analysis,  385 

Lead-chamber  gases,  336 

Level  of  water,  correct  reading  of,  32 

Level-tube  for  gas-volumeters,  24 

Liquid  admixtures  in  gases,  114 

Liquefied  gases,  357 

Litre,  the  true,  38 

Litre-weights  of  gases,  388 

Low  temperatures,  separation  of  gases  by 

it,  178 

Lunge-Orsat  apparatus,  71 
Lux  gas-balance,  183 

MANOMETERS,  188 

differential,  189 
Measuring  gases,  17 
apparatus  for,  30 
calibration,  31 
Mechanical   reduction    of   gas-volumes   to 

the  normal  state,  19 
Meniscus-correction,  31,  34 
for  mercury,  42,  43 
difference  of  corrections  for  water  and 

mercury,  46 
Mercaptan,  354 

Mercury  as  confining-liquid,  42 
meniscus  corrections,  43 
weights  of  a  cubic  centimetre  at  different 

temperatures,  45 

difference    of   meniscus    corrections    of 
water  against  mercury,  46 


INDEX  OF  SUBJECTS 


405 


Mercury,  estimation  of  mercurial  vapours 

in  air,  115,  353 

Methane,  estimation,  71,  75,  90,  92,  109, 
152,  153,  154,  156,  158,  164,  167,  170, 
172,  173,  175.  266 
its  estimation  in  the  absence  of  hydrogen, 

(fire-damp),  161,  267 
in  the  presence  of  hydrogen,  162 
qualitative  reaction,  271 
estimation  of  very  small  quantities,  272 
"  Metrogas  "  apparatus,  176 
Minimetric  method,  142 
Minute    quantities    of    gases,  estimation, 

142,  145 
Moisture  in  gases,  115 

NAPHTHALENE  vapour,  estimation,  298 
Nickel-cyanide  solution,  ammoniacal,  108 
Nitric  oxide,  absorbents  for,  128 

estimation  by  oxidation,  317,  318 

by  reaction    with   hydrogen   or   carbon 
monoxide,  319 

in    mixtures    containing    also    nitrogen 

protoxide,  320,  341 
Nitrogen,  absorbing  agents  for,  128 

calculation  in  gas-analysis,  161,  175 

combustion,  172 

estimation  of  free  nitrogen,  321,  325 
Nitrogen  oxides,  formation  in  combustion 

pipettes,  93 

Nitrogen  peroxide,  322,  341 
Nitrogen  protoxide,  314,  320 

together    with    nitric    oxide    and    free 
nitrogen,  321 

liquefied,  analysis,  367 
Nitrogen  trioxide,  322 
Nitroglycerine,  314 
Nitrometer,  Lunge's,  372 

other  forms,  379 

provided   with   a  separate  decomposing 
bottle,  381 

applications,  384 

modifications,  385 
Nitrous  gases  and  fumes,  192,  323 
Normal  volume  of  gases,  2 

correcting  the  readings  for  it,  17 
formula  for  this,  18 

mechanical  reduction  for  it,  19 

readily  filled  reduction  tubes,  26 

tables  for  reducing  gas  volumes  to   the 
normal  state,  382 


OPTICAL  methods  for  gas  analysis,  176 
Orsat's  apparatus,  66 

similar  apparatus,  70 

Lunge's  modification,  71 

other  modifications,  76,  393 

for  estimation  of  oxygen,  337 
Ostwald  pipette,  37 
Oxygen,  estimation,  55,  64,  69,  89,  152,  211 

generation,  97 

compressed,  analysis,  368 
Ozone,  detection,  219 

estimation,  220 

PALLADIUM   as   absorbent   for    hydrogen, 
129 

its  catalytic  action,  1 68 
Palladium  asbestos,  164,  165 
Palladium  hydrosol,  131 
Palladium  tubes,  Bunte's,  169 
Pfeiffer's  gas-analytical  apparatus,  103 

his  explosion  pipette,  163 
Phosphorus  as  absorbent  for  oxygen,  119 
Phosphorus  trichloride,  352 
Photometers,  2  r  I 
Pipes   for  aspirating  gas  samples,  4.     See 

Tubes 
Pipettes,  Ostwald's,  37 

improved  form,  38 

Hempel's,  84 

Platinum  for  the  combustion  of  gases,  164 
Platinum  wire  for  burning  methane,  92 

colloidal       platinum       for       absorbing 

hydrogen,  131 
Porcelain  tubes  for  gases,  4 
Pressure-gauges,  188 
Producer-gas,  356 
Pyridine,  327,  362 
Pyrogallol  as  absorbent  for  oxygen,  122 

QUARTZ  tubes,  5,  276 

REDUCTION  tubes  for  gas-volumes  to  the 
normal  state,  21 

filled  ready  for  sale,  26 

by  tables,  382 
Referees'  method  for  sulphur  in  coal-gas, 

257 

Refractometer,  Haber's,  176 
Rotameter,  50 

SAMPLING  of  gases,  3 

place  at  which  the  sample  is  taken,  3 
removal  of  air,  4 


406 


INDEX  OF  SUBJECTS 


Sampling  aspirating-tubes,  4.     See  Tubes 
by  blowers,  9 
by  steam  jets,  9 

by  Bunsen  pumps,  10 
by  water-jet  pumps,  n 
by  aspirating-bottles,  13 
automatic  gas-samplers,  14,  393 
sampling    of    compressed   or    liquefied 

gases,  358 

vessels  for  carrying  gas  samples,  393 
Sar co-calorimeter,  210 
Schlagwetterpfeife,  277 
Smoke-gases,  356 
Sodium    hydrosulphite    as   absorbent    for 

oxygen,  125 

Solid  admixtures  in  gases,  112 
Solubility  of  gases  in  water,  31 
Soot,  114 

Specific  gravity  of  gases,  178 
calculation  from  analysis,  179 
determination  by  measuring  the  velocity 
of    gases    when    issuing    from    an 
orifice,  180 

apparatus  of  Schilling,  181 
gas  balance  of  Lux,  183 
other  apparatus,  186 
estimating  the  specific  gravity  of  gases 

in  motion,  187,  393 
estimating  it   for  the   determination   of 

calorific  power,  192 
Sprengel  pump,  10 
Standard  solutions  for   gas-analysis,  133, 

391 

Standard    temperature  and   pressure    for 

measuring  gases,  192 
Steam-jet  aspirator  for  gases,  9 
Stopcocks  of  glass,  lubrication,  15 
Straight-edge  for  reading  burettes,  33 
Sulphur,  loss  in  the  exit-gases,  342 
Sulphur,  total  in  coal-gas,  149,  245,  257 
Sulphur  compounds,  organic,  253 
Sulphur  dioxide,  estimation  by  the  appar- 
atus of  Hesse,  135 

of  Reich,  137 

of  Lunge  and  Zeckendorff,  142 

of  Ost  and  Wislicenus,  150 

of  Ljungh,  243 

in  vitriol-chamber  gases,  244 

by  specific  gravity,  etc.,  246 

alongside  with  sulphur  trioxide,  247 

in   presence  of  sulphuretted  hydrogen, 
252 


Sulphur    dioxide,    liquefied,    examination, 

361 

Sulphur  trioxide,  estimation,  142,  247 
Sulphuretted  compounds,  organic,  253 
Sulphuretted  hydrogen,  detection,  248 

estimation,  gravimetric,  249 

volumetric,  2$o 

colorimetric,  251 

in  presence  of  sulphur  dioxide,  252 
Sulphuric  acid  in  gases,  116 

in  acid  smoke,  150 

in  the  presence  of  sulphur  dioxide,  247 
Sulphuric  acid  manufacture,  gases,  336 
Sulphuric     acid,     fuming,    as    absorbing- 
agent,  118 
Sulphurous  acid.     See  Sulphur  dioxide 

TAR  vapours  in  coal-gas,  305 
Temperature  of  the  gas-analytical  labora- 
tory, 1 8 
reduction     of    gas-volumes    for    normal 

temperature,  18 
automatic  elimination  of  its  influence  in 

gas-balances,  21 

corrections  for  tables  in  calibrating  gas- 
measuring  apparatus,  39 
tables  for  this,  40,  41 
Ten-bulb  tube,  146 

Titration  of  the  constituents  of  gases,  132 
general  remarks,  132 
apparatus  for  it,  133 
apparatus  of  Hesse,  135 

of  Reich,  modified  by  Lunge,  137 
minimetric  method,  142 
Tobacco  smoke,  355 
Tubes  for  aspirating  gas-samples,  4 
where  to  place  them,  5 
for  hot  gases,  5 
for  Bessemer  converters,  5 
cooling  arrangements,  6,  7,  8 
metallic  tubes,  6 

for  inaccessible  places,  8 
measuring  the  volume  of  gases  while 

passing  through  tubes,  50 
Lunge's  ten-bulb  tube,  146 

VESSELS     for     collecting,     keeping,     and 

carrying  gases,  14,  393 
made  of  india-rubber,  15 

of  glass,  15 
stopcocks,  15 


INDEX  OF  SUBJECTS 


407 


Visierblende,  33 

Vitriol-chamber  gases,  336 

Volume    of    gases,   correcting   it    for    the 

normal  state,  17 
formula  for  it,  18 
mechanical  reduction  to  the  normal 

state,  19 

formulae  for  the  gas-volumeter,  24 
correction  for  aqueous  vapour,  24 
readily  tilled  reduction  tubes,  26 
reduction    to    normal  temperature,   39, 

40,41 

tables    for    reducing  it   to   the    normal 
state,  382 


Volumes  of  gases,  changes  when  they  are 

burnt  in  oxygen,  389 
Volumes  of  water  at  I5°-3O°,  36 

WATER  as  confining-liquid  for  gases,  30 
solubility  of  gases  in  water,  31 
correct  reading  of  the  level,  32 

Water-air  pumps  (Sprengel   or    Bunsen), 
for  aspirating  gases,  10 

Water-gas,  356 

Water-jet  pumps,  II,  1 2 

Weight,  estimation  of  gases  by,  147 

Winkler  coil,  14$ 

Winkler  burette  modified,  84 


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Barker,  A.  H.     Graphic  Methods  of  Engine  Design i2mo,  *i  50 

• Heating  and  Ventilation 4to,  *8  oo 

Barnard,  J.  H.     The  Naval  Militiaman's  Guide i6mo,  leather  i  oo 

Barnard,  Major  J.  G.     Rotary  Motion.     (Science  Series  No.  90.) i6mo,  051 

Barrus,  G.  H.     Boiler  Tests 8vo,  *3  oo 

• Engine  Tests 8vo,  *4  oo 

The  above  two  purchased  together *6  OP 

Barwise,  S.     The  Purification  of  Sewage i2tr>o,  3  50 

Baterden,  J.  R.     Timber.     (Westminster  Series.) 8*0,  *2  oo 

Bates,  E.  L.,  and  Charlesworth,  F.     Practical  Mathematics i2mo, 

Part   I.    Preliminary  and  Elementary  Course . .  *i  50 

Part  II.    Advanced  Course *i  5^ 

Practical  Mathematics i2mo,  *i  50 

Practical  Geometry  and  Graphics i2mo,  *2  oo 

Beadle,  C.     Chapters  on  Papermaking.     Five  Volumes i2mo,  each,  *2  oo 

Beaumont,  R.     Color  in  Woven  Design 8vo,  *6  oo 

Finishing  of  Textile  Fabrics 8vo,  *4  co 

Beaumont,  W.  W.     The  Steam-Engine  Indicator 8vo,  2  50 

Bechhold,   H.     Colloids  in   Biology   and   Medicine.     Trans,   by   J.    G. 

Bullowa (In  Press.) 

Beckwith,  A.     Pottery 8vo,  paper,  o  60 

Bedell,  F.,  and  Pierce,  C.  A.    Direct  and  Alternating  Current  Manual. 

8vo,  *2  oo 

Beech,  F.     Dyeing  of  Cotton  Fabrics 8vo,  *3  oo 

Dyeing  of  Woolen  Fabrics 8vo,  *3  50 

Begtrup,  J.     The  Slide  Valve 8vo,  *2  oo 

Beggs,  G.  E.    Stresses  in  Railway  Girders  and  Bridges (In  Press.) 

Bender,  C.  E.     Continuous  Bridges.     (Science  Series  No.  26.) i6mo,  050 

Proportions  of  Piers  used  in  Bridges.     (Science  Series  No.  4.) 

i6mo,  o  50 

Bennett,  H.  G.     The  Manufacture  of  Leather 8vo,  *4  50 

Leather  Trades    (Outlines  of  Industrial   Chemistry).    8vo.  .(In  Press.) 

Bernthsen,    A.      A  Text  -  book  of  Organic  Chemistry.      Trans,  by  G. 

M'Gowan i2mc,  *2  50 

Berry,  W.  J.    Differential  Equations  of  the  First  Species.    i2mo.  (In  Preparation.) 
Bersch,  J.     Manufacture  of  Mineral  and  Lake  Pigments.     Trans,  by  A.  C. 

Wright 8vo,  *5  co 

Berlin,  L.  E.     Marine  Boilers.     Trans,  by  L.  S.  Robertson .8vo,  5  oo 

Beveridge,  J.     Papermaker's  Pocket  Book izmo,  *4  on 

Binnie,  Sir  A.     Rainfall  Reservoirs  and  Water  Supply 8vo,  *s  oo 

Binns,  C.  F.     Ceramic  Technology 8vo,  *5  oo 

Manual  of  Practical  Potting 8vo,  *7  50 

The  Potter's  Craft i2mo,  *2  oo 

"Birchmore,  W.  H.    Interpretation  of  Gas  Analysis I2mo,  *i  25 

Elaine,  R.  G.    The  Calculus  and  Its  Applications i2mo,  *i  So 

Blake,  W.  H.    Brewers'  Vade  Mecum 8vo,  *4  oo 

Blasdale,  W.  C.    Quantitative  Chemical  Analysis lamo.  (In  Press.) 

Bligh,  W.  G.    The  Practical  Design  of  Irrigation  Works 8vo,  *6  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG          5 

Bloch,  L.     Science  of  Illumination.     Tran-5.  by  W.  C.  Clinton &TO,  "2  50 

Blok,  A.     Illumination  and  Artificial  Lighting i2mo,  i  25 

Bliicher,  H.     Modern  Industrial  Chemistry.     Trans,  by  J.  P.  Millington. 

hvo,  *7  50 

Blyth,  A.  W.     Foods:  Their  Composition  and  Analysis 8vo,  7  50- 

—  —  Poisons:  Their  Effects  and  Detection .    8vo,  7  50 

Bockmann,  F.     Celluloid i2mo,  *2  50 

Bodmer,  G.  R.     Hydraulic  Motors  and  Turbines i2mo,  5  oo 

Boileau,  J.  T.     Traverse  Tables 8vo,  5  oo 

Bonney,  G.  E.     The  Electro-platers'  Handbook i2mo,  i  20 

Booth,  N.     Guide  to  the  Ring-spinning  Frame i2mo,  *i  25 

Booth,  W.  H.     Water  Softening  and  Treatment 8vo,  *2  50 

Superheaters  and  Superheating  and  Their  Control 8vo,  *i  50 

Bottcher,  A.     Cranes:    Their  Construction,  Mechanical  Equipment  and 

Working.     Trans,  by  A.  Tolhausen 4to,  *io  oo 

Bottler,  M.     Modern  Bleaching  Agents.    Trans,  by  C.  Salter.  .  .  .i2mo,  *2  50 

Bottone,  S.  R.     Magnetos  for  Automobilists i2mo,  *i  oo 

Boulton,  S.  B.     Preservation  of  Timber.    (Science  Series  No.  82.) .  i6mo,  o  50 

Bourcart,  E.     Insecticides,  Fungicides  and  Weedkillerc 8vo,  *4  50 

Bourgougnon,  A.    Physical  Problems.    (Science  Series  No.  113.) .  i6mo,  050 
Bourry,  E.     Treatise  on  Ceramic  Industries.     Trans,  by  A.  B.  Searle. 

8vo,  *s  oo 

Bow,  R.  H.    A  Treatise  on  Bracing 8vo,  i  50 

Bowie,  A.  J.,  Jr.     A  Practical  Treatise  on  Hydraulic  Mining 8vo,  5  oo 

Bowker,  W.  R.     Dynamo,  Motor  and  Switchboard  Circuits 8vo,  *2  50 

Bowles,  O.    Tables  of  Common  Rocks.    (Science  Series  No.  125.). i6mo,  050 

Bowser,  E.  A.     Elementary  Treatise  on  Analytic  Geometry i2mo,  i  75 

Elementary  Treatise  on  the  Differential  and  Integral  Calculus .  1 2 mo,  2  25 

Elementary  Treatise  on  Analytic  Mechanics i2mo,  3  oo 

Elementary  Treatise  on  Hydro-mechanics 12 mo,  2  50 

A  Treatise  on  Roofs  and  Bridges i2mo,  *2  25 

Boycott,  G.  W.  M.     Compressed  Air  Work  and  Diving 8vo,  *4 .  oo 

Bragg,  E.  M.     Marine  Engine  Design i2mo,  *2  oo 

Brainard,  F.  R.     The  Sextant.     (Science  Series  No.  101.) i6mo, 

Brassey's  Naval  Annual  for  1911 8vo,  *6  oo 

Brew,  W.     Three-Phase  Transmission 8vo,  *2  oo 

Briggs,  R.,  and  Wolff,  A.  R.     Steam-Heating.     (Science  Series  No. 

67.) i6mo,  o  50 

Bright,  C.     The  Life  Story  of  Sir  Charles  Tilson  Bright 8vo,  *4  50 

Erislee,  T.  J.     Introduction  to  the  Study  of  Fuel.     (Outlines  of  Indus- 
trial Chemistry.) 8vo,  *3  oo 

Broadfoot,  S.  K.     Motors,  Secondary  Batteries.     (Installation  Manuals 

Series.) ismo,  *o  75 

Broughton,  H.  H.    Electric  Cranes  and  Hoists *g  oo 

Brown,  G.     Healthy  Foundations.     (Science  Series  No.  80.) i6mo,  o  50 

Brown,  H.     Irrigation 8vo,  *5  oo 

Brown,  Wm.  N.     The  Art  of  Enamelling  on  Metal i2mo,  *i  oo 

Handbook  on  Japanning  and  Enamelling i2mo,  *i  50 

House  Decorating  and  Painting i2mo,  *i  50 

• History  of  Decorative  Art i2mo,  *i  25 


6          D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Brown,    Wm.    N.      Dipping,    Burnishing,    Lacquering    and    Bronzing 

Brass  Ware * i2mo,  *i  oo 

Workshop  Wrinkles 8vo,  *i  oo 

Browne,  C.  L.    Fitting  and  Erecting  of  Engines 8vo,  *i  50 

Browne,  R.  E.    Water  Meters.     (Science  Series  No.  81.) i6mo,  o  50 

Bruce,  E.  M.     Pure  Food  Tests lamo,  *i  25 

Bruhns,  Dr.     New  Manual  of  Logarithms 8vo,  cloth,  2  oo 

half  morocco,  2  50 
Brunner,  R.     Manufacture  of  Lubricants,  Shoe  Polishes  and  Leather 

Dressings.     Trans,  by  C.  Salter 8vo,  *3  oo 

Buel,  R.  H.     Safety  Valves.     (Science  Series  No.  21.) i6mo,  o  50 

Burns,  D.     Safety  in  Coal  Mines i2mo,  *i  oo 

Burstall,  F.  W.     Energy  Diagram  for  Gas.     With  Text 8vo,  i  50 

Diagram.     Sold  separately *i  oo 

Burt,  W.  A.    Key  to  the  Solar  Compass i6mo,  leather,  2  5 ) 

Burton,  F.  G.     Engineering  Estimates  and  Cost  Accounts i2mo,  *i  50 

Buskett,   E.  W.     Fire   Assaying i2mo,  *i  25 

Butler,  H.  J.     Motor  Bodies  and  Chassis 8vo,  *2  50 

Byers,  H.  G.,  and  Knight,  H.  G.     Notes  on  Qualitative  Analysis  ....  8vo,  *i  50 

Cain,  W.    Brief  Course  in  the  Calculus i2mo,  *i  75 

Elastic  Arches.     (Science  Series  No.  48.) i6mo,  o  50 

Maximum  Stresses.     (Science  Series  No.  38.) i6mo,  o  50 

Practical  Designing  Retaining  of  Walls.     (Science  Series  No.  3.) 

i6mo,  o  50 
Theory    of    Steel-concrete    Arches    and    of    Vaulted     Structures. 

(Science  Series  No.  42.) i6mo,  o  50 

Theory  of  Voussoir  Arches.     (Science  Series  No.  12.) i6mo,  o  50 

• Symbolic  Algebra.     (Science  Series  No.  73.) i6mo,  o  50 

Campin,  F.     The  Construction  of  Iron  Roofs 8vo,  2  oo 

Carpenter,  F.  D.   Geographical  Surveying.    (Science  Series  No.  37.). i6mo, 

Carpenter,  R.  C.,  and  Diederichs,  H.     Internal  Combustion  Engines. .  8vo,  *5  oo 

Carter,  E.  T.     Motive  Power  and  Gearing  for  Electrical  Machinery .  8vo,  *5  oo 

Carter,  H.  A.    Ramie  (Rhea),  China  Grass i2mo,  *2  oo 

Carter,  H.  R.     Modern  Flax,  Hemp,  and  Jute  Spinning 8vo,  *3  oo 

Gary,  E.  R.     Solution  of  Railroad  Problems  with  the  Slide  Rule.  .  i6mo,  *i  oo 

Cathcart,  W.  L.     Machine  Design.     Part  I.  Fastenings 8vo,  *3  oo 

Cathcart,  W.  L.,  and  Chaffee,  J.  I.     Elements  of  Graphic  Statics .  .  .8vo,  *3  oo 

Short  Course  in  Graphics I2mo,  I  50 

Caven,  R.  M.,  and  Lander,  G.  D.     Systematic  Inorganic  Chemistry.  i2mo,  *2  oo 

Chalkley,  A.  P.     Diesel  Engines 8vo,  *3  oo 

Chambers'  Mathematical  Tables Svo,  i  75 

Chambers,  G.  F.     Astronomy , i6mo,  *i  50 

Charpentier,  P.     Timber Svo,  *6  oo 

Chatley,  H.     Principles  and  Designs  of  Aeroplanes.     (Science   Series 

No.  126) i6mo,  o  50 

• How  to  Use  Water  Power .  , i2mo,  *i  oo 

' Gyrostatic  Balancing Svo,  *i  oo 

Child,  C.  D.     Electric  Arc Svo,  *2  oo 

Child,  C.  T.     The  How  and  Why  of  Electricity i2mo,  i  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG          7 

Christian,    M.      Disinfection    and    Disinfectants.      Trans,     by    Chas. 

Salter 12010,  200 

Christie,  W.  W.     Boiler-waters,  Scale,  Corrosion,  Foaming 8vo,  *3  oo 

Chimney  Design  and  Theory 8vo,  *3  OD 

Furnace  Draft.     (Science  Series  No.  123.) i6mo,  050 

Water:  Its  Purification  and  Use  in  the  Industries 8vo,  *2   co 

Church's  Laboratory  Guide.     Rewritten  by  Edward  Kinch 8vo,  *2  50 

Clapperton,  G.     Practical  Papermaking 8vo,  2  50 

Clark,  A.  G.     Motor  Car  Engineering. 

Vol.    I.     Construction *3  oo 

Vol.  II.     Design , (In  Press.) 

Clark,  C.  H.     Marine  Gas  Engines i2mo,  *i  50 

Clark,  D.  K.     Fuel:   Its  Combustion  and   Economy i2mo,  i  50 

Clark,  J.  M.     New  System  of  Laying  Out  Railway  Turnouts i2mo,  i  oo 

Clausen-Thue,  W.     ABC  Telegraphic  Code.     Fourth  Edition  . .  .  i2mo,  *5  oo 

Fifth  Edition 8vo,  *7  oo 

-  The  A  i  Telegraphic  Code 8vo,  *7  50 

Clerk,  D.,  and  Idell,  F.  E.     Theory  of  the  Gas  Engine.     (Science  Series 

No.  62.) i6mo,  o  50 

Clevenger,  S.  R.     Treatise  on  the  Method  of  Government  Surveying. 

i6mo,    morocco,  2  50 

Clouth,  F.     Rubber,  Gutta-Percha,  and  Balata 8vo,  *5  o^ 

Cochran,  J.    Concrete  and  Reinforced  Concrete  Specifications 8vo,  *2  50 

-  Treatise  on  Cement  Specifications 8vo,  *i  oo 

Coffin,  J.  H.  C.     Navigation  and  Nautical  Astronomy i2mo,  *3  50 

Colburn,  Z.,  and  Thurston,  R.  H.     Steam  Boiler  Explosions.     (Science 

Series  No.  2.) i6mo,  o  50 

Cole,  R.  S.     Treatise  on  Photographic  Optics i2mo,  150 

Coles-Finch,  W.     Water,  Its  Origin  and  Use 8vo,  *5  oo 

Collins,  J.  E.     Useful  Alloys  and  Memoranda  for  Goldsmiths,  Jewelers. 

i6mo,  o  50 

Collis,  A.  G.     High  and  Low  Tension  Switch-Gear  Design 8vo,  *s  53 

—  Switchgear.      (Installation   Manuals   Series.) i2mo,  *o  50 

Constantine,  E.   Marine  Engineers,  Their  Qualifications  and  Duties. .  8vo,  *2  oo 

Coombs,  H.  A.     Gear  Teeth.     (Science  Series  No.  120.) i6mo,  o  50 

Cooper,  W.  R.     Primary  Batteries 8vo,  *4  oo 

"  The  Electrician  "  Primers 8vo,  *$  oo 

Part  I ^ *i  50 

Part  II *2  50 

Part  III *2  oo 

Copperthwaite,  W.  C.     Tunnel  Shields .410,  *g  OD 

Corey,  H.  T.     Water  Supply  Engineering 8vo  (In  Press.) 

Corfield,  W.  H.     Dwelling  Houses.     (Science  Series  No.  50.) ....  i6mo,  o  50 

Water  and  Water-Supply.     (Science  Series  No.  17.) i6mo,  o  50 

Cornwall,  H.  B.     Manual  of  Blow-pipe  Analysis 8vo,  *2  50 

Courtney,  C.  F.     Masonry  Dams 8vo,  3  50 

Cowell,  W.  B.     Pure  Air,  Ozone,  and  Water i2mo,  *2  oo 

Craig,  T.     Motion  of  a  Solid  in  a  Fuel.     (Science  Series  No.  49.) .  i6mo,  o  50 
Wave  and  Vortex  Motion.     (Science  Series  No.  43.)  i6mo,  o  50 


8         D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Cramp,  W.     Continuous  Current  Machine  Design 8vo,  *2  50 

Greedy,  F.     Single  Phase  Commutator  Motors 8vo,  *2  oo 

Crocker,  F.  B.     Electric  Lighting.     Two  Volumes.     8vo. 

Vol.   I.     The  Generating  Plant 3  o  > 

Vol.  II.     Distributing  Systems  and  Lamps 

Crocker,  F.  B.,  and  Arendt,  M.     Electric  Motors 8vo,  *2  50 

Crocker,  F.  B.,  and  Wheeler,  S.  S.    The  Management  of  Electrical  Ma- 
chinery   i2mo,  *i  oo 

Cross,  C.  F.,  Bevan,  E.  J.,  and  Sindall,  R.  W.     Wood  Pulp  and  Its  Applica- 
tions.    (Westminster  Series.) .8vo,  *2  oo 

Crosskey,  L.  R.     Elementary  Perspective 8vo,  i  oo 

Crosskey,  L.  R.,  and  Thaw,  J.     Advanced  Perspective 8vo,  i  50 

Culley,  J.  L.     Theory  of  Arches.     (Science  Series  No.  87.) i6mo,  o  $a 

Dadourian,  H.  M.     Analytical  Mechanics i2mo,  *3  oo 

Danby,  A.    Natural  Rock  Asphalts  and  Bitumens 8vo,  *2  50 

Davenport,  C.     The  Book.     (Westminster  Series.) 8vo,  *2  oo 

Davies,  D.  C.    Metalliferous  Minerals  and  Mining 8vo,  5  oo 

Earthy  Minerals  and  Mining 8vo,  5  oo 

Davies,  E.  H.     Machinery  for  Metalliferous  Mines 8vo,  8  oo 

Davies,  F.  H.    Electric  Power  and  Traction 8vo,  *2  oo 

Foundations  and  Machinery  Fixing.     (Installation  Manual  Series.) 

i6mo,  *i  oo 

Dawson,  P.    Electric  Traction  on  Railways 8vo,  *g  oo 

Day,  C.    The  Indicator  and  Its  Diagrams i2mo,  *2  oo 

Deerr,  N.     Sugar  and  the  Sugar  Cane 8vo,  *8  oo 

Deite,  C.     Manual  of  Soapmaking.     Trans,  by  S.  T.  King 4to,  *5  oo 

De  la  Coux,  H.    The  Industrial  Uses  of  Water.    Trans,  by  A.  Morris.  8vo,  *4  50 

Del  Mar,  ,W.  A.    Electric  Power  Conductors 8vo,  *2  oo 

Denny,  G.  A.    Deep-level  Mines  of  the  Rand 4to,  *io  oo 

Diamond  Drilling  for  Gold *5  oo 

De  Roos,  J.  D.  C.     Linkages.     (Science  Series  No.  47.) i6mo,  o  50 

Derr,  W.  L.    Block  Signal  Operation Oblong  i2mo,  *i  50 

Maintenance-of-Way  Engineering (In  Preparation.} 

Desaint,  A.     Three  Hundred  Shades  and  How  to  Mix  Them 8vo,  *io  oo 

De  Varona,  A.     Sewer  Gases.     (Science  Series  No.  55.) i6mo,  o  50 

Devey,  R.  G.     Mill  and  Factory  Wiring.     (Installation  Manuals  Series.) 

i2mo,  *i  oo 

Dibdin,  W.  J.     Public  Lighting  by  Gas  and  Electricity 8vt,  *8  oo 

Purification  of  Sewage  and  Water 8vo,  6  50 

Dichmann,  Carl.     Basic  Open-Hearth  Steel  Process i2mo,  *3  50 

Dieterich,  K.     Analysis  of  Resins,  Balsams,  and  Gum  Resins 8vo,  *3  oo 

Dinger,  Lieut.  H.  C.     Care  and  Operation  of  Naval  Machinery  .  . .  i2mo,  *2  oo 
Dixon,  D.  B.     Machinist's  and  Steam  Engineer's  Practical  Calculator. 

i6mo,  morocco,  i  25 

Doble,  W.  A.     Power  Plant  Construction  on  the  Pacific  Coast  (In  Press.) 

Dommett,  W.  E.     Motor  Car  Mechanism i2mo,  *i  25 

Dorr,  B.  F.     The  Surveyor's  Guide  and  Pocket  Table-book. 

i6mo,  morocco,  2  oo 

Down,  P.  B.    Handy  Copper  Wire  Table  .  . i6mo,  *i  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  9 

Draper,  C.  H.     Elementary  Text-book  of  Light,  Heat  and  Sound  .  .  i2mo,  i  oo 

Heat  and  the   Principles   of   Thermo-dynamics i2mo,  *2  oo 

Dubbel,  H.    High  Power  Gas  Engines (In  Press.) 

Duckwall,  E.  W.     Canning  and  Preserving  of  Food  Products 8vo,  *5  oo 

Dumesny,  P.,  and  Noyer,  J.    Wood  Products,  Distillates,  and  Extracts. 

8vo,  *4  50 
Duncan,  W.  G.,  and  Penman,  D.     The  Electrical  Equipnisnt  of  Collieries. 

8vo,  *4  OD 
Dunstan,  A.  E.,  and  Thole,  F.  B.  T.     Textbook  of  Practical  Chemistry. 

i2mo,  *i  40 

Duthie,  A.  L.     Decorative  Glass  Processes.     (Westminster  Series.)  .8vo,  *2  oo 

Dwight,  H.  B.     Transmission  Line  Formulas 8vo,  *2  oo 

Dyson,  S.  S.     Practical  Testing  of  Raw  Materials 8vo,  *5  oo 

Dyson,  S.  S.,  and  Clarkson,  S.  S.     Chemical  Works 8vo,  *7  50 

Eccles,  R.  G.,  and  Duckwall,  E.  W.     Food  Preservatives . . .  .8vo,  paper,  o  50 
Eck,  J.     Light,  Radiation  and  Illumination.     Trafcs.  by  Paul  Hogner, 

8yo,  *2  50 

Eddy,  H.  T.    Maximum  Stresses  under  Concentrated  Loads 8vo,  i  50 

Edelman,  P.  Inventions  and  Patents i2mo.  (In  Press.) 

Edgcumbe,  K.     Industrial  Electrical  Measuring  Instruments 8vo,  *2  50 

Edler,  R.     Switches  and  Switchgear.     Trans,  by  Ph.  Laubach. .  .8vo,  *4  oo 

Eissler,  M.     The  Metallurgy  of  Gold 8vo,  7  50 

The  Hydrometallurgy  of  Copper 8vo,  *4  50 

The  Metallurgy  of  Silver 8vo,  4  oo 

The  Metallurgy  of  Argentiferous  Lead 8vo,  5  oo 

A  Handbook  on  Modern  Explosives .  .  8vo,  5  oo 

Ekin,  T.  C.     Water  Pipe  and  Sewage  Discharge  Diagrams folio,  *3  oo 

Eliot,  C.  W.,  and  Storer,  F.  H.     Compendious  Manual  of  Qualitative 

Chemical  Analysis 12010,  *i  25 

Ellis,  C.    Hydrogenation  of  Oils 8vo.   ( /;/  Press. ) 

Ellis,  G.     Modern  Technical  Drawing 8vo,  *2  oo 

Ennis,  Wm.  D.    Linseed  Oil  and  Other  Seed  Oils 8vo,  *4  oo 

Applied  Thermodynamics 8vo,  *4  50 

Flying  Machines  To-day i2mo,  *4  50 

Vapors  for  Heat  Engines i2mo,  *i  oo 

Erfurt,  J.     Dyeing  of  Paper  Pulp.     Trans,  by  J.  Hubner 8vo,  *7  50 

Ermen,  W.  F.  A.     Materials  Used  in  Sizing 8vo,  *2  oo 

Evans,  C.  A.     Macadamized  Roads (In  Press.) 

Ewing,  A.  J.     Magnetic  Induction  in  Iron 8vo,  *4  oo 

Fairie,  J.     Notes  on  Lead  Ores i2mo,  *i  oo 

—  Notes    on   Pottery    Clays izmo,  *i  50 

Fan-ley,  W.,  and  Andre,  Geo.  J.    Ventilation  of  Coal  Mines.     (Science 

Series  No.  58.) i6mo,  o  50 

Fairweather,  W.  C.     Foreign  and  Colonial  Patent  Laws 8vo,  *3  oo 

Fanning,  J.  T.     Hydraulic  and  Water-supply  Engineering 8vo,  *5  oo 

Fauth,  P.    The  Moon  in  Modern  Astronomy.    Trans,  by  J.  McCabe. 

8vo,  *2  oo 


10       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Fay,  I.  W.     The  Coal-tar  Colors 8vo,  *4  oo 

Fernbach,  R.  L.     Glue  and  Gelatine 8vo,  *3  oo 

Chemical  Aspects  of  Silk  Manufacture i2mo,  *i  oo 

Fischer,  E.     The  Preparation  of  Organic  Compounds.     Trans,  by  R.  V. 

Stanford „ i2mo,  *i  25 

Fish,  J.  C.  L.     Lettering  of  Working  Drawings Oblong  8vo,  i  oo 

Fisher,  H.  K.  C.,  and  Darby,  W.  C.     Submarine  Cable  Testing  .  . .  .8vo,  *3  50 
Fleischmann,  W.    The  Book  of  the  Dairy.    Trans,  by  C.  M.  Aikman. 

8vo,  4  oo 
Fleming,  J.  A.    The  Alternate-current  Transformer.     Two  Volumes.  8vo. 

Vol.   I.    The  Induction  of  Electric  Currents *5  oo 

Vol.  II.     The  Utilization  of  Induced  Currents *5  oo 

Fleming,  J.  A.    Propagation  of  Electric  Currents 8vo,  *3  oo 

Centenary  of  the  Electrical  Current 8vo,  *o  50 

Electric  Lamps  and  Electric  Lighting 8vo,  *3  oo 

Electrical  Laboratory  Notes  and  Forms .  . 4to,  *s  oo 

A  Handbook  for  the  Electrical  Laboratory  and  Testing  Room.     Two 

Volumes 8vo,  each,  *5  oo 

Fleury,  P.    Preparation  and  Uses  of  White  Zinc  Paints 8vo,  *2  50 

Fleury,  H.     The  Calculus  Without  Limits  or  Infinitesimals.     Trans,  by 

C.  O.  Mailloux (In  Press.) 

Flynn,  P.  J.    Flow  of  Water.     (Science  Series  No.  84.) i2mo,  o  50 

Hydraulic  Tables.     (Science  Series  No.  66.) i6mo,  o  50 

Foley,  N.    British  and  American  Customary  and  Metric  Measures .  .  folio,  *3  oo 

Forgie,  J.     Shield  Tunneling 8vo.    (In  Press.) 

Foster,  H.  A.    Electrical  Engineers'  Pocket-book.      (Seventh  Edition.) 

i2mo,  leather,  5  oo 

Engineering  Valuation  of  Public  Utilities  and  Factories 8vo,  *3  oo 

Handbook  of  Electrical  Cost  Data 8vo  (In  Press.) 

Foster,  Gen.  J.  G.     Submarine  Blasting  in  Boston  (Mass.)  Harbor    4 to,  3  53 

Fowle,  F.  F.     Overhead  Transmission  Line  Crossings i2mo,  *i  50 

The  Solution  of  Alternating  Current  Problems 8vo  (In  Press.) 

Fox,  W.  G.     Transition  Curves.     (Science  Series  No.  no.) i6mo,  050 

Fox,  W.,  and  Thomas,  C.  W.     Practical  Course  in  Mechanical  Draw- 
ing   i2mo,  i  25 

Foye,  J.  C.     Chemical  Problems.     (Science  Series  No.  69.) i6mo,  o  50 

Handbook  of  Mineralogy.     (Science  Series  No.  86.) i6mo,  o  50 

Francis,  J.  B.    Lowell  Hydraulic  Experiments 4to,  15  oo 

Franzen,  H.     Exercises  in  Gas  Analysis i2mo,  *i  oo 

Freudemacher,   P.   W.    Electrical   Mining  Installations.     (Installation 

Manuals  Series.) i2mo,  *i  oo 

Frith,  J.    Alternating  Current  Design 8vo,  *2  oa 

Fritsch,  J.    Manufacture  of  Chemical  Manures.    Trans,  by  D.  Grant. 

8vo,  *4  oo 

Frye,  A.  I.    Civil  Engineers'  Pocket-book i2mo,  leather,  *5  oo 

Fuller,  G.  W.     Investigations  into  the  Purification  of  the  Ohio  River. 

4to,  *io  oo 

Furnell,  J.    Paints,  Colors,  Oils,  and  Varnishes 8vo.  *i  oo 

Gairdner,  J.  W.  I.    Earthwork 8vo  (In  Press.) 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  11 

Gant,  L.  W.     Elements  of  Electric  Traction 8vo,  *2  50 

Garcia,  A.  J.  R.  V.     Spanish-English  Railway  Terms 8vo,  *4  50 

Garforth,  W.  E.     Rules  for  Recovering  Coal  Mines  after  Explosions  and 

Fires i2mo,  leather,  i  50 

Gaudard,  J.     Foundations.     (Science  Series  No.  34.) i6mo,  050 

Gear,  H.  B.,  and  Williams,  P.  F.     Electric  Central  Station  Distribution 

Systems 8vo,  *3  oa 

Geerligs,  H.  C.  P.     Cane  Sugar  and  Its  Manufacture 8vo,  *5  oo 

World's  Cane  Sugar  Industry 8vo,  *5  oo 

Geikie,  J.     Structural  and  Field  Geology 8vo,  *4  oo 

—  Mountains.     Their   Growth,    Origin  and   Decay 8vo,  *4  oo 

The  Antiquity  of  Man  in  Europe 8vo.  (In  Press.} 

Gerber,  N.   Analysis  of  Milk,  Condensed  Milk,  and  Infants' Milk-Food.    8vo,  i  25 
Gerhard,  W.  P.     Sanitation,  Watersupply  and  Sewage  Disposal  of  Country 

Houses 1 2mo,  *a  oo 

Gas  Lighting      (Science  Series  No.  in.) i6mo,  o  50 

Household  Wastes.     (Science  Series  Ho.  97.) i6mo,  o  50 

House  Drainage.     (Science  Series  No.  63.) i6mo,  o  30 

Gerhard,  W.  P.     Sanitary  Drainage  of  Buildings.    (Science  Series  No.  93.) 

i6mo,  o  50 

Gerhardi,  C.  W.  H.     Electricity  Meters 8vo,  *4  oo 

Geschwind,   L.     Manufacture   of  Alum   and   Sulphates.     Trans,    by  C. 

Salter 8vo,  *$  oo 

Gibbs,  W.  E.     Lighting  by  Acetylene i2mo,  *i  50 

Physics  of  Solids  and  Fluids.     (Carnegie  Technical  School's  Text- 
books.)   *i  50 

Gibson,  A.  H.     Hydraulics  and  Its  Application 8vo,  *s  oo 

Water  Hammer  in  Hydraulic  Pipe  Lines i2mo,  *2  oo 

Gilbreth,  F.  B.     Motion  Study i2mo,  *2  oo 

Primer  of  Scientific  Management i2mo,  *i  oo 

Gillxnore,  Gen.  Q.  A.     Limes,  Hydraulic  Cements  and  Mortars 8vo,  4  oo 

Roads,  Streets,  and  Pavements i2mo,  2  oo 

Golding,  H.  A.     The  Theta-Phi  Diagram i2mo,  *i  25 

Goldschmidt,  R.     Alternating  Current  Commutator  Motor 8vo,  *3  oo 

Goodchild,  W.     Precious  Stones.     (Westminster  Series.) 8vo,  *2  oo 

Goodeve,  T.  M.     Textbook  on  the  Steam-engine 12  mo,  2  oo 

Gore,  G.     Electrolytic  Separation  of  Metals 8vo,  *3  50 

Gould,  E.  S.     Arithmetic  of  the  Steam-engine I2mo,  i  oo 

Calculus.     (Science  Series  No.  112.) i6mo,  o  50 

High  Masonry  Dams.     (Science  Series  No.  22.) i6mo,  o  50 

Practical  Hydrostatics  and  Hydrostatic  Formulas.     (Science  Series 

No.  117.) i6mo,  o  50 

Gratacap,  L.  P.     A  Popular  Guide  to  Minerals 8vo,  *3  o° 

Gray,  J.     Electrical  Influence  Machines i2mo,  2  oo 

Marine  Boiler  Design 12010,  *i  25 

Greenhill,  G.     Dynamics  of  Mechanical  Flight 870,  *2  50 

Greenwood,  E.     Classified  Guide  to  Technical  and  Commercial  Books.  870,  *3  oo 

Gregorius,  R.     Mineral  Waxes.     Trans,  by  C.  Salter i2mo,  *3  oo 

Griffiths,  A.  B.     A  Treatise  on  Manures 12010,  3  oo 

Dental  Metallurgy 8vo,  *3  50 


12        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Gross,  E.     Hops 8vo,  *4  50 

Grossman,  J.     Ammonia  and  Its  Compounds i2mo,  *i  25 

Groth,  L.  A.     Welding  and  Cutting  Metals  by  Gases   or  Electricity. 

(Westminster  Series) 8vo,  *2  oo 

Grover,  F.     Modern  Gas  and  Oil  Engines 8vo,  *2  oo 

Gruner,  A.     Power-loom  Weaving 8vo,  *3  oo 

Giildner,  Hugo.     Internal  Combustion  Engines.     Trans,  by  H.  Diederichs. 

4to,  *io  oo 

Gunther,  C.  0.     Integration. ..., i2mo,  *i  25 

Gurden,  R.  L.     Traverse  Tables folio,  half  morocco,  *y  50 

Guy,  A,  E.     Experiments  on  the  Flexure  of  Beams 8vo,  *i  25 

Haeder,    H.      Handbook   on    the    Steam-engine.      Trans,  by  H.  H.  P. 

Powles i2mo,  3  oo 

Hainbach,  R.     Pottery  Decoration.     Trans,  by  C.  Salter i2mo,  *3  oo 

Haenig,  A.    Emery  and  Emery  Industry 8vo,  *2  50 

Hale,  W.  J.     Calculations  of  General  Chemistry i2mo,  *i  oo 

Hall,  C.  H.     Chemistry  of  Paints  and  Paint  Vehicles i2mo,  *2  oo 

Hall,  G.  L.    Elementary  Theory  of  Alternate  Current  Working 8vo,  *i  50 

Hall,  R.  H.     Governors  and  Governing  Mechanism i2mo,  *2  oo 

Hall,  W.  S.     Elements  of  the  Differential  and  Integral  Calculus 8vo,  *2  25 

Descriptive  Geometry 8vo  volume  and  a  410  atlas,  *3  50 

Haller,  G.  F.,  and  Cunningham,  E.  T.     The  Tesla  Coil i2mo,  *i  25 

Halsey,  F.  A.     Slide  Valve  Gears i2mo,  i  50 

The  Use  of  the  Slide  Rule.     (Science  Series  No.  114.) i6mo,  o  50 

Worm  and  Spiral  Gearing.     (Science  Series  No.  116.). ; i6mo,  o  50 

Hamilton,  W.  G.     Useful  Information  for  Railway  Men i6mo,  i  oo 

Hammer,  W.  J.     Radium  and  Other  Radio-active  Substances 8vo,  *i  co 

Hancock,  H.     Textbook  of  Mechanics  and  Hydrostatics 8vo,  i  50 

Hardy,  E.     Elementary  Principles  of  Graphic  Statics 12010,  *i  50 

Harris,  S.  M.    Practical  Topographical  Surveying (In  Press.) 

Harrison,  W.  B.     The  Mechanics'  Tool-book i2mo,  i  50 

Hart,  J.  W.     External  Plumbing  Work 8vo,  *3  oo 

Hints  to  Plumbers  on  Joint  Wiping 8vo,  *3  oo 

Principles  of  Hot  Water  Supply 8vo,  *3  oo 

Sanitary  Plumbing  and  Drainage 8vo,  *3  oo 

Haskins,  C.  H.     The  Galvanometer  and  Its  Uses i6mo,  i  50 

Hatt,  J.  A.  H.     The  Colorist square  i2mo,  *i  50 

Hausbrand,  E.     Drying  by  Means  of  Air  and  Steam.     Trans,  by  A.  C. 

Wright i2mo,  *2  oo 

Evaporating,  Condensing  and  Cooling  Apparatus.     Trans,  by  A.  C. 

Wright 8vo,  *s  oo 

Hausner,  A.     Manufacture  of  Preserved  Foods  and  Sweetmeats.     Trans. 

by  A.  Morris  and  H.  Robson 8vo,  *3  oo 

Hawke,  W.  H.     Premier  Cipher  Telegraphic  Code 4to,  *s  oo 

100,000  Words  Supplement  to  the  Premier  Code 4to,  *5  oo 

Hawkesworth,  J.     Graphical  Handbook  for  Reinforced  Concrete  Design. 

4to,  *2  50 

Hay,  A.     Alternating  Currents. 8vo,  *2  50 

Electrical  Distributing  Networks  and  Distributing  Lines 8vo,  *3  So 

Continuous  Current  Engineering 8vo,  *2  50 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  13 

Hayes,  H.  V.    Public  Utilities,  Their  Cost  New  and  Depreciation. .  .8vo,  *2  oo 

Heap,  Major  D.  P.     Electrical  Appliances 8vo,  2  oo 

Heather,  H.  J.  S.    Electrical  Engineering 8vo,  *3  50 

Heaviside,  O.     Electromagnetic  Theory.      Vols.  I  and  II. ..  .8vo,  each,  *5  oo 

Vol.  Ill 8vo,  *7   50 

Heck,  R.  C.  H.    The  Steam  Engine  and  Turbine 8vo,  *s  oo 

Steam-Engine  and  Other  Steam  Motors.    Two  Volumes. 

Vol.    I.     Thermodynamics  and  the  Mechanics 8vo,  *3  50 

Vol.  II.     Form,  Construction,  and  Working 8vo,  *5  OD 

Notes  on  Elementary  Kinematics 8vo,  boards,  *i  oo 

Graphics  of  Machine  Forces 8vo,  boards,  *i  oo 

Hedges,  K.     Modern  Lightning  Conductors 8vo,  3  oo 

Heermann,  P.     Dyers'  Materials.     Trans,  by  A.  C.  Wright i2mo,  *2  50 

Hellot,  Macquer  and  D'Apligny.  Art  of  Dyeing  Wool,  Silk  and  Cotton.  8vo,  *2  oo 

Henrici,  O.     Skeleton  Structures 8vo,  i  50 

Bering,  D.  W.    Essentials  of  Physics  for  College  Students 8vo,  *i  75 

Hering-Shaw,  A.     Domestic  Sanitation  and  Plumbing.     Two  Vols..  .8vo,  *5  oo 

Hering-Shaw,  A.    Elementary  Science 8vo,  *2  oa 

Herrmann,  G.     The  Graphical  Statics  of  Mechanism.     Trans,  by  A.  P. 

Smith 12010,  2  oo> 

Herzfeld,  J.     Testing  of  Yarns  and  Textile  Fabrics 8vo,  *3  53 

Hildebrandt,  A.     Airships,  Past  and  Present 8vo,  *3  50 

Hildenbrand,  B.  W.    Cable-Making.     (Science  Series  No.  32.). ..  .i6mo,  o  50 

Hilditch,  T.  P.     A  Concise  History  of  Chemistry i2mo,  *i  25 

Hill,  J.  W.    The  Purification  of  Public  Water  Supplies.    New  Edition. 

(In   Press.) 

Interpretation  of  Water  Analysis (In  Press.) 

Hill,  M.  J.  M.    The  Theory  of  Proportion 8vo,  *2  50 

Hiroi,  I.    Plate  Girder  Construction.     (Science  Series  No.  95.) . . .  i6mo,  o  50 

Statically-Indeterminate  Stresses i2tno,  *2  oo 

Hirshfeld,  C.  F.    Engineering  Thermodynamics.  (Science  Series  No.  45.) 

i6mo,  o  50 

Hobart,  H.  M.    Heavy  Electrical  Engineering 8vo,  *4  50 

Design  of  Static  Transformers i2mo, .  *2  oo 

Electricity 8vo,  *2  oo 

Electric  Trains 8vo,  *2  50 

Hobart,  H.  M.     Electric  Propulsion  of  Ships 8vo,  *2  oo 

Hobart,  J.  F.    Hard  Soldering,  Soft  Soldering  and  Brazing i2mo,  *i  oo 

Hobbs,  W.  R.  P.    The  Arithmetic  of  Electrical  Measurements. ..  .i2mo,  o  50 

Hoff,  J.  N.    Paint  and  Varnish  Facts  and  Formulas i2mo,  *x  50 

Hole,  W.    The  Distribution  of  Gas 8vo,  *7  50 

Holley,  A.  L.     Railway  Practice folio,  12  oo 

Holmes,  A.  B.    The  Electric  Light  Popularly  Explained. ..  i2mo,  paper,  o  50 

Hopkins,  N.  M.    Experimental  Electrochemistry 8vo,  *3  CD 

Model   Engines   and   Small   Boats i2mo,  i  25 

Hopkinson,  J.,  Shoolbred,  J.  N.,  and  Day,  R.  E.     Dynamic  Electricity. 

(Science  Series  No.  71.) i6mo,  o  50 

Homer,  J.    Metal  Turning i2mo,  i  50 

Modern  Ironf ounding i2mo,  *2  50 

Plating  and  Boiler  Making 8vo,  3  oo 

Eoughton,  C.  E.    The  Elements  of  Mechanics  of  Materials i2mo,  *2  oo 


I4        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Houllevigue,  L.     The  Evolution  of  the  Sciences 8vo,  *2  oo 

Houstoim,  R.  A.    Studies  in  Light  Production i2mo,      2  oo 

Howe,  G.     Mathematics  for  the  Practical  Man i2mo,  *i  25 

Howorth,  J.     Repairing  and  Riveting  Glass,  China  and  Earthenware. 

8vo,  paper,  *o  50 

Eubbard,  E.     The  Utilization  of  Wood-waste 8vo,  *2  50 

Hiibner,  J.   Bleaching  and  Dyeing  of  Vegetable  and  Fibrous  Materials. 

(Outlines  of  Industrial  Chemistry.) 8vo,  *s  oo 

Hudson,  0.  F.    Iron  and  Steel.    (Outlines  of  Industrial  Chemistry. ).8vo,  *2  oo 

Kumper,  W.     Calculation  of  Strains  in  Girders i2mo,      2  50 

Humphreys,  A.  C.    The  Business  Features  of  Engineering  Practice .  .8vo,  *i  25 

Hunter,  A.    Bridge  Work 8vo.  (In  Press.) 

Hurst,  G.  H.     Handbook  of  the  Theory  of  Color 8vo,  *2  50 

—  Dictionary  of  Chemicals  and  Raw  Products 8vo,  *s  oo 

—  Lubricating  Oils,  Fats  and  Greases 8vo,  *4  oo 

—  Soaps 8vo,  *5  oo 

Hurst,  G.  H.,  and  Simmons,  W.  H.    Textile  Soaps  and  Oils 8vo,  *2  50 

Hurst,  H.  E.,  and  Lattey,  R.  T.     Text-book  of  Physics 8vo,  *s  OD 

—  Also  published  in  three  parts. 

Part      I.    Dynamics  and  Heat *i  23 

Part    II.    Sound  and  Light *i  25 

Part  III.    Magnetism  and  Electricity *i  50 

Jlutchinson,  R.  W.,  Jr.    Long  Distance  Electric  Power  Transmission. 

i2mo,  *3  oc  • 

Kutchinson,  R.  W.,  Jr.,  and  Thomas,  W.  A.    Electricity  in  Mining.  i2mo, 

(In  Press.) 
Hutchinson,  W.  B.     Patents  and  How  to  Make  Money  Out  of  Them. 

I2IDO,          I    25 

Button,  W.  S.     Steam-boiler  Construction 8vo,      6  co 

Practical  Engineer's  Handbook 8vo,      7  oo 

—  The  Works'  Manager's  Handbook 8vo,      6  oo 

Hyde,  E.  W.     Skew  Arches.     (Science  Series  No.  15.) i6mo,      o  50 

Hyde,  F.  S.    Solvents,  Oils,  Gums,  Waxes 8vo,  *2  oo 

Induction  Coils.     (Science  Series  No.  53.) i6mo,  053 

Ingham,  A.  E.    Gearing.    A  practical  treatise (In  Press.) 

Ingle,  H.     Manual  of  Agricultural  Chemistry 8vo,  *3  oo 

Iiiness,  C.  H.    Problems  in  Machine  Design 12010,  *2  oo 

Air  Compressors  and  Blowing  Engines i2mo,  *2  oo 

—  Centrifugal  Pumps i2mo,  *2  oo 

The  Fan i2mo,  *2  oo 

Isherwood,  B.  F.    Engineering  Precedents  for  Steam  Machinery . .  .8vo,  2  50 

Ivatts,  E.  B.    Railway  Management  at  Stations 8vo,  *2  50 

Jacob,  A.,  and  Gould,  E.  S.  On  the  Designing  and  Construction  of 

Storage  Reservoirs.  (Science  Series  No.  6) i6mo,  o  50 

Jannettaz,  E.  Guide  to  the  Determination  of  Rocks.  Trans,  by  G.  W. 

Plympton i2mo,  i  50 

Jehl,  F.     Manufacture  of  Carbons .8vo,  *4  oo 

Jennings,  A.  S.  Commercial  Paints  and  Painting.  (Westminster  Series.) 

8vo,  *2  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  15 

Jennison,  F.  H.     The  Manufacture  of  Lake  Pigments 8vo,  *3  oo 

Jepson,  G.     Cams  ana  the  Principles  of  their  Construction 8vo,  *i  50 

—  Mechanical  Drawing 8vo  (In  Preparation.) 

Jockin,  W.     Arithmetic  of  the  Gold  and  Silversmith i2mo,  *i  oo 

Johnson,  J.  H.     Arc  Lamps  and  Accessory  Apparatus.     (Installation 

Manuals  Series.) , .  i2mo,  *o  75 

Johnson,  T.  M.     Ship  Wiring  and  Fitting.     (Installation  Manuals  Series.) 

i2mo,  *o  75 

Johnson,  W.  H.    The  Cultivation  and  Preparation  of  Para  Rubber . .  8vo,  *3  oo 

Johnson,  W.  McA.     The  Metallurgy  of  Nickel (In  Preparation.) 

Johnston,  J.  F.  W.,  and  Cameron,  C.     Elements  of  Agricultural  Chemistry 

and  Geology i2mo,  2  60 

Joly,  J.    Radioactivity  and  Geology i2mo,  '3  oo 

Jones,  H.  C.     Electrical  Nature  of  Matter  and  Radioactivity i2mo,  *2  oo 

—  New  Era  in  Chemistry i2mo,  *2  oo 

Jones,  M.  W.     Testing  Raw  Materials  Used  in  Paint i2mo,  *2  oo 

Jones,  L.,  and  Scard,  F.  I.     Manufacture  of  Cane  Sugar ; . . . .  8vo,  *5  oo 

Jordan,  L.  C.     Practical  Railway  Spiral i2mo,  leather,  *i  50 

Joynson,  F.  H.     Designing  and  Construction  of  Machine  Gearing  .  .  8vo,  2  oo 

Jiiptn«r,  H.  F.  V.     Siderology :  The  Science  of  Iron 8vo,  *5  oo 

Kansas  City  Bridge 4to,  6  oo 

Kapp,  G.     Alternate  Current  Machinery.     (Science  Series  No.  96.). i6mo,  050 

Keim,  A.  W.     Prevention  of  Dampness  in  Buildings 8vo,  *2  oo 

Keller,  S.  S.     Mathematics  for  Engineering  Students.     1 2mo,  half  leather. 

Algebra  and  Trigonometry,  with  a  Chapter  on  Vectors *i  75 

Special  Algebra  Edition *i .  oo 

Plane  and  Solid  Geometry *i .  25 

Analytical  Geometry  and  Calculus *2  oo 

Kelsey,  W.  R.     Continuous-current  Dynamos  and  Motors t8vo,  *2  50 

Kemble,  W.  T.,  and  Underbill,  C.  R.    The  Periodic  Law  and  the  Hydrogen 

Spectrum 8vo,  paper,  *o  50 

Kemp,  J.  F.    Handbook  of  Rocks 8vo,  *i  50 

Kendall,  E.     Twelve  Figure  Cipher  Code 4to,  *i2  50 

Kennedy,  A.  B.  W.,  and  Thurston,  R.  H.     Kinematics  of  Machinery. 

(Science  Series  No.  54.) i6mo,  o  50 

Kennedy,  A.  B.  W.,  Unwin,  W.  C.,  and  Idell,  F.  E.     Compressed  Air. 

(Science  Series  No.  106.) i6mo,  o  50 

Kennedy,  R.     Modern  Engines  and  Power  Generators.  Six  Volumes.  4to,  15  oo 

Single  Volumes each,  3  oo 

Electrical  Installations.     Five  Volumes 4to,  15  oo 

Single  Volumes each,  3  50 

Flying  Machines;  Practice  and  Design i2mo,  *2  -oo 

Principles  of  Aeroplane  Construction 8vo,  *i  50 

Kennelly,  A.  E.     Electro-dynamic  Machinery 8vo,  i  50 

Kent,  W.     Strength  of  Materials.     (Science  Series  No.  41.) i6mo,  o  50 

Kershaw,  J.  B.  C.     Fuel,  Water  and  Gas  Analysis 8vo,  *2  50 

Electrometallurgy.     (Westminster  Series.) 8vo,  *2  oo 

The  Electric  Furnace  in  Iron  and  Steel  Production i2mo,  *i  50 

Electro-Thermal    Methods    of   Iron   and   Steel   Production 8vo,     *3  OD 


16       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Kinzbrunner,  C.     Alternate  Current  Windings 8vo,  *i  50 

Continuous  Current  Armatures , 8vo,  *i  50 

—  Testing  of  Alternating  Current  Machines 8vo,  *2  oo 

Kirkaldy,  W.  G.    David  Kirkaldy's  System  of  Mechanical  Testing.  .4to,  10  oo 

Kirkbride,  J.     Engraving  for  Illustration 8vo,  *i  50 

Kirkwood,  J.  P.     Filtration  of  River  Waters 4to,  750 

Kirschke,  A.     Gas  and  Oil  Engines i2ma,  *i  25 

Klein,  J.  F.     Design  of  a  High-speed  Steam-engine 8vo,  *5  oo 

Physical  Significance  of  Entropy 8vo,  *i  50 

Kleinhans,  F.  B.    Boiler  Construction 8vo,  3  oo 

Knight,  R.-Adm.  A.  M.     Modern  Seamanship 8vo,  *7  50 

Half  morocco *9  oo 

Knox,  J.     Physico-Chemical  Calculations i2mo,  *i  oo 

— — Fixation     of     Atmospheric     Nitrogen.       (Chemical     Monographs, 
No.  4.) i2mo.   (In  Press.) 

Knox,  W.  F.     Logarithm  Tables (In  Preparation.) 

Knott,  C.  G.,  and  Mackay,  J.  S.     Practical  Mathematics 8vo,  2  oo 

Koester,  F.     Steam-Electric  Power  Plants 4to,  *5  oo 

Hydroelectric  Developments  and  Engineering 4to,  *5  oo 

Koller,  T.     The  Utilization  of  Waste  Products 8vo,  *s  50 

• Cosmetics 8vo,  *2  50 

Kremann,  R.     Application  of  the  Physico-Chemical  Theory  to  Tech- 
nical  Processes   and   Manufacturing  Methods.     Trans,   by  H. 

E.  Potts 8vo,  *3  oo 

Kretchmar,  K.     Yam  and  Warp  Sizing 8vo,  *4  oo 

Lallier,  E.  V.    Elementary  Manual  of  the  Steam  Engine i2mo,  *2  oo 

Lambert,  T.    Lead  and  Its  Compounds 8vo,  *3  50 

Bone  Products  and  Manures 8vo,  *3  oo 

Lamborn,  L.  L.     Cottonseed  Products 8vo,  *3  oo 

Modern  Soaps,  Candles,  and  Glycerin 8vo,  *7  50 

Lamprecht,  R.     Recovery  Work  After  Pit  Fires.   Trans,  by  C.  Salter .  8vo,  *4  oo 
Lancaster,  M.    Electric  Heating,  Cooking,  Cleaning.  .i2mo.  (In  Press.) 

Lanchester,  F.  W.    Aerial  Flight.     Two  Volumes.     8vo. 

Vol.  I.     Aerodynamics *6  oo 

Aerial  Flight.    Vol.  H.    Aerodonetics *6.  oo 

Lamer,  E.  T.     Principles  of  Alternating  Currents i2mo.  *i  25 

Larrabee,  C.  S.     Cipher  and  Secret  Letter  and  Telegraphic  Code.  i6mo,  o  60 

La  Rue,  B.  F.     Swing  Bridges.     (Science  Series  No.  107.) i6mo,  o  50 

Lassar-Cohn.  Dr.     Modern  Scientific   Chemistry.     Trans,   by   M.   M. 

Pattison  Muir i2mo,  *2  oo 

Latimer,  L.  H.,  Field,  C.  J.,  and  Howeli,  J.  W.     Incandescent  Electric 

Lighting.     (Science  Series  No.  57.)     : .  .j6mo,  o  50 

Latta,  M.  N.     Handbook  of  American  Gas-Engineering  Practice  . . .  8vo,  *4  50 

American  Producer  Gas  Practice 4*o»  *6  °° 

Lawson,   W.    R.     British   Railways.     A   Financial    and    Commercial 

Survey 8vo,  200 

Leask,  A.  R.    Breakdowns  at  Sea i2mo,  2  oo 

Refrigerating  Machinery i2mo,  2  oo 

Lecky,  S.  T.  S.     "  Wrinkles  "  in  Practical  Navigation 8vo,  *8  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG        17 

Le  Doux,  M.     Ice-Making  Machines.     (Science  Series  No.  46.) .  .  i6mo,      o  50 
Leeds,  C.  C.     Mechanical  Drawing  for  Trade  Schools oblong   4to, 

High  School  Edition *i  25 

Machinery  Trades  Edition .  . *2 .00 

LefSvre,  L.    Architectural  Pottery.    Trans,  by  H.  K.  Bird  and  W.  M. 

Binns 4to,     *7  50 

Lehner,  S.     Ink  Manufacture.     Trans,  by  A.  Morris  and  H.  Robson .  8vo,     *2  50 

Lemstrom,  S.     Electricity  in  Agriculture  and  Horticulture 8vo,    *i  50 

Letts,  E.  A.     Fundamental  Problems  in  Chemistry 8vo,    *2  oo 

Le  Van,  W.  B.    Steam-Engine  Indicator.    (Science  Series  No.  78.)i6mo,      o  50 
Lewes,  V.  B.     Liquid  and  Gaseous  Fuels.     (Westminster  Series.).  .8vo,     *2  oo 

Carbonization  of  Coal 8vo,     *3  oo 

Lewis,  L.  P.     Railway  Signal  Engineering 8vo,     *3  50 

Lieber,  B.  F.    Lieber's  Standard  Telegraphic  Code 8vo,  *io  oo 

Code.     German  Edition 8vo,  *io  eo 

—  Spanish  Edition 8vo,  *io  oo 

French  Edition 8vo,  *io  oo 

Terminal  Index 8vo,     *2  50 

Lieber's  Appendix folio,  *i$  oo 

Handy  Tables 4to,     *2  50 

Bankers  and  Stockbrokers'  Code  and  Merchants  and  Shippers' 

Blank  Tables 8vo,  "15  oo 

100,000,000  Combination  Code 8vo,  *io  oo 

Engineering  Code 8vo,  *I2  50 

Livennore,  V.  P.,  and  Williams,  J.    How  to  Become  a  Competent  Motor- 
man  1 2mo,     *i  oo 

Liversedge,  A.  J.     Commercial  Engineering 8vo,     *3  oo 

Livingstone,  R.    Design  and  Construction  of  Commutators 8vo,     *2  25 

Mechanical  Design  and  Construction  of  Generators . 8vo.  (In  Press.} 

Lobben,  P.     Machinists'  and  Draftsmen's  Handbook 8vo,  2  50 

Lockwood,  T.  D.    Electricity,  Magnetism,  and  Electro-telegraph 8vo,  2  50 

L->ckwood,  T.  D.    Electrical  Measurement  and  the  Galvanometer. 

i2mo,  o  75 

Lodge,  O.  J.  Elementary  Mechanics i2mo,  i  50 

Signalling  Across  Space  without  Wires 8vo,  *2  oo 

Loewenstein,  L.  C.,  and  Crissey,  C.  P.     Centrifugal  Pumps *4  50 

Lord,  R.  T.     Decorative  and  Fancy  Fabrics 8vo,  *3  50 

Loring,  A.  E.    A  Handbook  of  the  Electromagnetic  Telegraph ....  i6mo  o  50 

• Handbook.     (Science  Series  No.  39.) i6mo,  o  50 

Low,  D.  A.    Applied  Mechanics  (Elementary) : . .  i6mo,  o  83 

Lubschez,  B.  J.    Perspective i2mo,  *i  50 

Lucke,  C.  E.     Gas  Engine  Design 8vo,  *3  oo 

Power  Plants:   Design,  Efficiency,  and  Power  Costs.     2  vols. 

(In  Preparation.) 

Lunge,  G.     Coal-tar  and  Ammonia.    Two  Volumes 8vo,  *i$  OD 

Manufacture  of  Sulphuric  Acid  and  Alkali.     Four  Volumes.  . .  .8vo, 

Vol.     I.     Sulphuric  Acid.     In  three  parts *i8  oo 

Vol.  n.     Salt  Cake,  Hydrochloric  Acid  and  Leblanc  Soda.    In  two 

parts *i5  •  ofr 


l8       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Lunge,  G.     Manufacture  of  Sulphuric  Acid  and  Alkali. 

Vol.  III.     Ammonia  Soda *io  on 

Vol.  IV.     Electrolytic  Methods (In  Press.} 

Technical  Chemists'  Handbook , i2mo,  leather,  *3  50 

Technical  Methods  of  Chemical  Analysis.     Trans,  by  C.  A.  Keane 

in  collaboration  with  the  corps  of  specialists. 

Vol.     I.     In  two  parts 8vo,   *i$  03 

Vol.   II.     In  two  parts 8vo,   *i8  03 

Vol.  Ill (In  Preparation.) 

Lupton,  A.,  Parr,  G.  D.  A.,  and  Perkin,  H.     Electricity  as  Applied  to 

Mining 8vo,  *4  50 

Luquer,  L.  M.     Minerals  in  Rock  Sections 8vo,  *i  50 

Macewen,  H.  A.     Food  Inspection 8vo,  *2  50 

Mackenzie,  N.  F.     Notes  on  Irrigation  Works .8vo,  *2  50 

Mackie,  J.    How  to  Make  a  Woolen  Mill  Pay 8vo,  *2  oo 

Mackrow,  C.     Naval  Architect's  and  Shipbuilder's  Pocket-book. 

i6mo,  leather,  5  oo 

Maguire,  Wm.  R.    Domestic  Sanitary  Drainage  and  Plumbing  .  .  .  .8vo,  4  oo 
Mallet,  A.     Compound  Engines.     Trans,  by  R.  R.  Buel.     (Science  Series 

No.  io.) i5mo, 

Mansfield,  A.  N.     Electro-magnets.     (Science  Series  No.  64.)  .  ..i6mo,  050 

Marks,  E.  C.  R.     Construction  of  Cranes  and  Lifting  Machinery  .12010,  *i  50 

Construction  and  Working  of  Pumps 12010,  *i  50 

Manufacture  of  Iron  and  Steel  Tubes 12010,  *2  oo 

Mechanical  Engineering  Materials i2mo,  *i  oo 

Marks,  G.  C.     Hydraulic  Power  Engineering 8vo,  3  50 

Inventions,  Patents  and  Designs i2mo,  *i  oo 

Marlow,  T.  G.    Drying  Machinery  and  Practice 8vo,  *5  oo 

Marsh,  C.  F.     Concise  Treatise  on  Reinforced  Concrete 8vo,  *2  50 

Reinforced  Concrete  Compression  Member  Diagram.     Mounted  on 

Cloth  Boards *i .  50 

Marsh,  C.  F.,  and  Dunn,  W.     Manual  of  Reinforced  Concrete  and  Con- 
crete Block  Construction i6mo,  morocco,  *2  50 

Marshall,  W.  J.,  and  Sankey,  H.  R.     Gas  Engines.     (Westminster  Series.) 

8vo,  *2  oo 

Martin,  G.     Triumphs  and  Wonders  of  Modern  Chemistry 8vo,  *2  oo 

Martin,  N.     Properties  and  Design  of  Reinforced  Concrete i2mo,  *2  50 

Massie,  W.  W.,  and  Underbill,  C.  R.     Wireless  Telegraphy  and  Telephony. 

i2mo,  *i  oo 
Matheson,D.   Australian  Saw-Miller's  Log  and  Timber  Ready  Reckoner. 

I2mo,  leather,  i  50 

Mathot,  R.  E.     Internal  Combustion  Engines .  . . . : 8vo,  *6  oo 

Maurice,  W.    Electric  Blasting  Apparatus  and  Explosives 8vo,  *3  50 

Shot  Firer's  Guide 8vo,  *i  50 

Maxwell,  J.  C.     Matter  and  Motion.     (Science  Series  No.  36.). 

i6mo,  o  50 

Maxwell,  W.  H.,  and  Brown,  J.  T.    Encyclopedia  of  Muncipal  and  Sani- 
tary Engineering 4to,  *io  oo 

Mayer,  A.  M.    Lecture  Notes  on  Physics 8vo,  2  oo 

McCullough,  R.  S.     Mechanical  Theory  of  Heat 8vo,  3  50 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  19 

Mclntcsh,  J.  G.     Technology  of  Sugar 8vo,  *4  50 

Industrial  Alcohol 8vo,  *3  oo 

Manufacture  of  Varnishes  and  Kindred  Industries.    Three  Volumes. 

8vo. 

Vol.     I.     Oil  Crushing,  Refining  and  Boiling *3  50 

Vol.    II.    Varnish  Materials  and  Oil  Varnish  Making *4  oo 

Vol.  III.     Spirit  Varnishes  and  Materials '. . .  *4  50 

McKnight,  J.  D.,  and  Brown,  A.  W.     Marine  Multitubular  Boilers *i  5 J 

McMaster,  J.  B.     Bridge  and  Tunnel  Centres.     (Science  Series  No.  20.) 

i6mo,  o  50 

McMechen,  F.  L.     Tests  for  Ores,  Minerals  and  Metals i2mo,  *i  oo 

McPherson,  J.  A.     Water-works  Distribution 8vo,  2  50 

Melick,  C.  W.     Dairy  Laboratory  Guide i2mo,  *i  25 

Merck,  E.     Chemical  Reagents;  Their  Purity  and  Tests.     Trans,  by 

H.  E.  Schenck 8vo,  i  oo 

Merivale,  J.  H.     Notes  and  Formulae  for  Mining  Students i2mo,  i  50 

Merritt,  Wm.  H.    Field  Testing  for  Gold  and  Silver i6mo,  leather,  i  50 

Messer,  W.  A.     Railway  Permanent  Way 8vo  (In  Press.) 

Meyer,  J.  G.  A.,  and  Pecker,  C.  G.     Mechanical  Drawing  and  Machine 

Design 4to,  5  oo 

Michell,  S.     Mine  Drainage 8vo,  10  oo 

Mierzinski,  S.     Waterproofing  of  Fabrics.     Trans,  by  A.  Morris  and  H. 

Robson 8vo,  *2  50 

Miller,  G.  A.     Determinants.     (Science  Series  No   105.) i6mo, 

Milroy,  M.  E.  W.     Home  Lace-making I2mo,  *i  oo 

Minifie,  W.     Mechanical  Drawing 8vo,  *4  oo 

Mitchell,  C.  A.     Mineral  and  Aerated  Waters 8vo,  *3  oo 

Mitchell,  C.  A.,  and  Prideaux,  R.  M.     Fibres  Used  in  Textile  and  Allied 

Industries 8vo,  *3  oo 

Mitchell,  C.  F.,  and  G.  A.     Building  Construction  and  Drawing.     i2mo. 

Elementary  Course *i  50 

Advanced  Course ." *2  50 

Monckton,  C.  C.  F.     Radiotelegraphy.     (Westminster  Series.) 8vo,  *2  oo 

Monteverde,  R.  D.     Vest  Pocket  Glossary  of  English-Spanish,  Spanish- 
English  Technical  Terms 64mo,  leather,  *i  oo 

Montgomery,  J.  H.     Electric   Wiring  Specifications (In   Press.) 

Moore,  E.  C.  S.     New  Tables  for  the  Complete  Solution  of  Ganguillst  and 

Kutt  ;r's  Formula 8vo,  *5  oo 

Morecroft,  J.  H.,  and  Hehre,  F.  W.     Short  Course  in  Electrical  Testing. 

8vo,  *i  50 
Moreing,  C.  A.,  and  Neal,  T.     New  General  and  Mining  Telegraph  Code. 

8vo,  *5  oo 

Morgan,  A.  P.     Wireless  Telegraph  Apparatus  for  Amateurs 12 mo,  *i  50 

Moses,  A.  J.     The  Characters  of  Crystals 8vo,  *2  oo 

and  Parsons,  C.  L.    Elements  of  Mineralogy 8vo,  *a  50 

Moss,  S. A.  Elementsof  Gas  Engine  Design. (Science  Series  No. 121.)  i6mo,  o  50 

The  Lay-out  of  Corliss  Valve  Gears.     (Science  Series  No.  119.)  i6mo,  o  50 

Mulford,  A.  C.     Boundaries  and  Landmarks i2mo,  *i  oo 

Mullin,  J.  P.     Modern  Moulding  and  Pattern-making i2mo,  250 


20       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Munby,  A.  E.     Chemistry  and  Physics  of  Building  Materials.     (West- 
minster Series.) 8vo,  *2  oo 

Murphy,  J.  G.     Practical  Mining i6mo,  i  co 

Murphy,  W.  S.    Textile  Industries.     Eight  Volumes *ao  oo 

Sold  separately,  each,  *3  oo 

Murray,  J.  A.     Soils  and  Manures.     (Westminster  Series.) 8vo,  *2  oo 

Naquet,  A.    Legal  Chemistry i2mo,  2  oo 

Nasmith,  J.     The  Student's  Cotton  Spinning 8vo,  3  oo 

Recent  Cotton  Mill  Construction i2mo,  2  oo 

Neave,  G.  B.,  and  Heilbron,  I.  M.     Identification  of  Organic  Compounds. 

i2mo,  *i  25 

Neilson,  R.  M.    Aeroplane  Patents 8vo,  *2  oo 

Nerz,  F.     Searchlights.     Trans,  by  C.  Rodgers 8vo,  *3  oo 

Neuberger,  H.,  and  Noalhat,  H.     Technology  of  Petroleum.     Trans,  by 

J.  G.  Mclntosh 8vo,  *io  oo 

Newall,  J.  W.    Drawing,  Sizing  and  Cutting  Bevel-gears 8vo,  i  50 

Nicol,  G.     Ship  Construction  and  Calculations 8vo,  *4  50 

Nipher,  F.  E.    Theory  of  Magnetic  Measurements i2mo,  i  oo 

Nisbet,  H.     Grammar  of  Textile  Design 8vo,  *3  oo 

Nolan,  H.    The  Telescope.     (Science  Series  No.  51.) i6mo,  o  50 

Noll,  A.     How  to  Wire  Buildings i2mo,  i  50 

North,  H.  B.    Laboratory  Experiments  in  General  Chemistry i2mo,  *i  oo 

Nugent,  E.     Treatise  on  Optics i2mo,  i  50 

O'Connor,  H.  The  Gas  Engineer's  Pocketbook i2mo,  leather,  3  50 

• Petrol  Air  Gas i2mo,  *o  75 

Ohm,  G.  S.,  and  Lockwood,  T.  D.  Galvanic  Circuit.  Translated  by 

William  Francis.  (Science  Series  No.  102.) i6mo,  o  50 

Olsen,  J.  C.  Text-book  of  Quantitative  Chemical  Analysis 8vo,  *4  oo 

Olsson,  A.  Motor  Control,  in  Turret  Turning  and  Gun  Elevating.  (U.  S. 

Navy  Electrical  Series,  No.  i.) i2mo,  paper,  *o  50 

Ormsby,  M.  T.  M.  Surveying i2mo,  i  50 

Oudin,  M.  A.     Standard  Polyphase  Apparatus  and  Systems 8vo,  *3  oo 

Owen,  D.     Recent  Physical  Research 8vo,  *i  50 

Pakes,  W.  C.  C.,  and  Nankivell,  A.  T.     The  Science  of  Hygiene  .  .8vo,  *i  75 

Palaz,  A.     Industrial  Photometry.     Trans,  by  G.  W.  Patterson,  Jr.  .  8vo,  *4  oo 

Pamely,  C.     Colliery  Manager's  Handbook 8vo,  *io  oo 

Parker,  P.  A.  M.    The  Control  of  Water 8vo,  *s  oo 

Parr,  G.  D.  A.    Electrical  Engineering  Measuring  Instruments. ..  .8vo,    *3  50 

Parry,  E.  J.     Chemistry  of  Essential  Oils  and  Artificial  Perfumes. .  .  8vo,  *5  oo 

Foods  and  Drugs.    Two  Volumes 8vo, 

Vol.   I.     Chemical  and  Microscopical  Analysis  of  Foods  and  Drugs.  *7  5° 

Vol.  II.     Sale  of  Food  and  Drugs  Act *3  oo 

and  Coste,  J.  H.     Chemistry  of  Pigments 8vo,  *4  50 

Parry,  L.  A.     Risk  and  Dangers  of  Various  Occupations 8vo,  *3  oo 

Parshall,  H.  F.,  and  Hobart,  H.  M.     Armature  Windings 4to,  *7  50 

Electric  Railway  Engineering 4*o,  *io  00^ 

• and  Parry,  E.     Electrical  Equipment  of  Tramways .  .  ( In  Press. ) 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  21 

Parsons,  S.  J.     Malleable  Cast  Iron 8vo,  *2  53 

Partington,  J.  R.    Higher  Mathematics  for  Chemical  Students.  .12010,  *2  oo 

Textbook  of  Thermodynamics 8vo,  *4  oo 

Passmore,  A.  C.     Technical  Terms  Used  in  Architecture 8vo,  *3  50 

Patchell,  W.  H.     Electric  Power  in  Mines 8vo,  *4  oo 

Paterson,  G.  W.  L.     Wiring  Calculations i2mo,  *2  oo 

Patterson,  D.     The  Color  Printing  of  Carpet  Yarns 8vo,  *3  50 

Color  Matching  on  Textiles 8vo,  ::  3  oo 

The  Science  of  Color  Mixing 8vo,  *3  oo 

Paulding,  C.  P.     Condensation  of  Steam  in  Covered  and  Bare  Pipes.  .8vo,  *2  oo 

Transmission  of  Heat  through  Cold-storage  Insulation 12010,  *i  oo 

Payne,   D.   W.     Iron  Founders'   Handbook (In   Press.) 

Peddie,  R.  A.     Engineering  and  Metallurgical  Books i2mo,  *i  50 

Peirce,  B.     System  of  Analytic  Mechanics 4to,  ID  oo 

Pendred,  V.     The  Railway  Locomotive.     (Westminster  Series.) 8vo,  *2  co 

Perkin,  F.  M.    Practical  Methods  of  Inorganic  Chemistry i2mo,  *i  oo 

Perrigo,  0.  E.     Change  Gear  Devices 8vo,  i  oo 

Perrine,  F.  A.  C.     Conductors  for  Electrical  Distribution 8vo,  *j  50 

Perry,  J.     Applied  Mechanics 8vo,  *2  50 

Petit,  G.     White  Lead  and  Zinc  White  Paints 8vo,  *i  50 

Petit,  R.     How  to  Build  an  Aeroplane.     Trans,  by  T.  O'B.  Hubbard,  and 

J.  H.  Ledeboer 8vo,  *i  50 

Pettit,  Lieut.  J.  S.     Graphic  Processes.     (Science  Series  No.  76.) . . .  i6mo,  o  50 
Philbrick,  P.  H.     Beams  and  Girders.     (Science  Series  No.  88.) . . .  i6mo, 

Phillips,  J.     Engineering  Chemistry 8vo,  *4  50 

Gold  Assaying 8vo,  *2  50 

Dangerous  Goods 8vo,  3  50 

Phin,  J.     Seven  Follies  of  Science '.  12010,  *i  25 

Pickworth,  C.  N.     The  Indicator  Handbook.     Two  Volumes.  .i2mo,  each,  150 

Logarithms  for  Beginners I2mo-  boards,  o  50 

The  Slide  Rule i2mo,  i  oo 

Plattner's  Manual  of  Blow-pipe  Analysis.    Eighth  Edition,  revised.    Trans. 

by  H.  B.  Cornwall 8vo,  *4  oo 

Plympton,  G.  W.    The  Aneroid  Barometer.    (Science  Series  No.  35.)    i6mo,  050 

How  to  become  an  Engineer^      (Science  Series  No.  100.) i6mo,  050 

Van  Nostrand's  Table  Book.      (Science  Series  No.  104.) i6mo,  050 

Pochet,  M.  L.     Steam  Injectors.     Translated  from  the  French.     (Science 

Series  No.  29.) i6mo,  o  50 

Pocket  Logarithms  to  Four  Places.     (Science  Series  No.  65.). . , i6mo,  o  50 

leather,  i  oo 

Polleyn,  F.     Dressings  and  Finishings  for  Textile  Fabrics 8vo,  *3  oo 

Pope,  F.  G.     Organic  Chemistry i2mo,  *2  25 

Pope,  F.  L.     Modern  Practice  of  the  Electric  Telegraph .  .8vo,  i  50 

Popple  well,  W.  C.  Elementary  Treatise  on  Heat  and  Heat  Engines .  .  12010,  *3  oo 

—  —  Prevention  of  Smoke 8vo,  *3  50 

Strength  of  Materials 8vo,  *i  75 

Porritt,   B.   D.     The   Chemistry   of    Rubber.      (Chemical   Monographs, 

No.  3.) i2mo,  *075 

Porter,  J.  R.     Helicopter  Flying  Machine 12010,  *i  25 

Potter,  T.     Concre!e 8vo,  *3  o» 


22        D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Potts,  H.  E.     Chemistry  of  the  Rubber  Industry.     (Outlines  of  Indus- 
trial Chemistry) 8vo,  *2  oo 

Practical  Compounding  of  Oils,  Tallow  and  Grease 8vo,  *3  50 

Practical  Iron  Founding i2mo,  i  50 

Pratt,  K.    Boiler  Draught i2mo,  *i  25 

Pray,  T.,  Jr.     Twenty  Years  with  the  Indicator 8vo,  2  50 

Steam  Tables  and  Engine  Constant 8vo,  2  oo 

Preece,  W.  H.     Electric  Lamps (In  Press.) 

Prelini,  C.     Earth  and  Rock  Excavation 8vo,  *3  oo 

Graphical  Determination  of  Earth  Slopes 8vo,  *2  oo 

Tunneling.    New  Edition 8vo,  *3  oo 

Dredging.    A  Practical  Treatise ,  .8vo,  *3  oo 

Prescott,  A.  B.     Organic  Analysis 8vo,  5  co 

Prescott,  A.  B.,  and  Johnson,  0.  C.     Qualitative  Chemical  Analysis.  .  .8vo,  *3  50 
Prescott,  A.  B.,  and  Sullivan,  E.  C.     First  Book  in  Qualitative  Chemistry. 

i2mo,  *i  50 

Prideaux,  E.  B.  R.    Problems  in  Physical  Chemistry 8vo,  *2  oo 

Pritchard,  0.  G.     The  Manufacture  of  Electric-light  Carbons .  .  8vo,  paper,  *o  60 
Pullen,  W.  W.  F.     Application  of  Graphic  Methods  to  the  Design  of 

Structures i2mo,  *2  50 

Injectors:  Theory,  Construction  and  Working I2mo,  *i  50 

Pulsifer,  W.  H.     Notes  for  a  History  of  Lead 8vo,  4  oo 

Purchase,  W.  R.     Masonry i2mo,  *3  oo 

Putsch,  A.     Gas  and  Coal-dust  Firing 8vo,  *3  oo 

Pynchon,  T.  R.     Introduction  to  Chemical  Physics 8vo,  3  oo 

Rafter  G.  W.     Mechanics  of  Ventilation.     (Science  Series  No.  33.) .  i6mo,  o  50 

—  Potable  Water.     (Science  Series  No.  103.) i6mo,  o  50 

Treatment  of  Septic  Sewage.     (Science  Series  No.  118.) . .  .i6mo,  o  50 

Rafter,  G.  W.,  and  Baker,  M.  N.     Sewage  Disposal  in  the  United  States. 

4to,  *6  oo 

Raikes,  H.  P.     Sewage  Disposal  Works 8vo,  *4  oo 

Randall,  P.  M.     Quartz  Operator's  Handbook 12 mo,  2  oo 

Randau,  P.     Enamels  and  Enamelling 8vo,  *4  oo 

Rankine,  W.  J.  M.     Applied  Mechanics 8vo,  5  oo 

Civil  Engineering 8vo,  6  50 

Machinery  and  Millwork 8vo,  5  oo 

The  Steam-engine  and  Other  Prime  Movers 8vo,  5  oo 

Useful  Rules  and  Tables 8vo,  4  oo 

JRankine,  W.  J.  M.,  and  Bamber,  E.  F.     A  Mechanical  Text-book 8vo,  3  50 

Raphael,  F.  C.     Localization  of  Faults  in  Electric  Light  and  Power  Mains. 

8vo,  *3  oo 

Rasch,  E.    Electric  Arc  Phenomena.    Trans,  by  K.  Tornberg 8vo,  *2  oo 

Rathbone,  R.  L.  B.     Simple  Jewellery 8vo,  *2  oo 

Rateau,  A.     Flow  of  Steam  through  Nozzles  and  Orifices.     Trans,  by  H. 

B.  Brydon 8vo  *i  50 

Rausenberger,  F.     The  Theory  of  the  Recoil  of  Guns 8vo,  *4  50 

Rautenstrauch,  W.    Notes  on  the  Elements  of  Machine  Design .  8  vo,  boards,  *  i  50 
Rautenstrauch,  W.,  and  Williams,  J.  T.     Machine  Drafting  and  Empirical 
Design. 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  23 

Part   I.  Machine  Drafting 8vo,  *i  25 

Part  II.  Empirical  Design (In  Preparation.) 

Raymond,  E.  B.     Alternating  Current  Engineering i2mo,  *2  50 

Rayner,  H.     Silk  Throwing  and  Waste  Silk  Spinning 8vo,  *2  50 

Recipes  for  the  Color,  Paint,  Varnish,  Oil,  Soap  and  Drysaltery  Trades .  8vo,  *3  50 

Recipes  for  Flint  Glass  Making i2mo,  *4  50 

Redfern,  J.  B.,  and  Savin,  J.    Bells,  Telephones  (Installation  Manuals 

Series.) i6mo,  *o  50 

Redgrove,  H.  S.     Experimental  Mensuration i2mo,  *x  25 

Redwood,  B.     Petroleum.     (Science  Series  No.  92.) i6mo,  o  50 

Reed,  S.    Turbines  Applied  to  Marine  Propulsion *5  oo 

Reed's  Engineers'  Handbook 8vo,  *5  oo 

Key  to  the  Nineteenth  Edition  of  Reed's  Engineers'  Handbook.  .8vo,  *3  oo 

Useful  Hints  to  Sea-going  Engineers i2mo,  i  50 

Marine  Boihrs i2mo,  2  oo 

• Guide  to  the  Use  of  the  Slide  Valve i2mo,  *i  60 

Reinhardt,  C.  W.     Lettering  for  Draftsmen,  Engineers,  and  Students. 

oblong  4to,  boards,  i  oo 

The  Technic  of  Mechanical  Drafting oblong  4to,  boards,  *i  oo 

Reiser,  F.     Hardening  and  Tempering  of  Steel.     Trans,  by  A.  Morris  and 

H.  Robson i2mo,  *2  50 

Reiser,  N.     Faults  in  the  Manufacture  of  Woolen  Goods.     Trans,  by  A. 

Morris  and  H.  Robson 8vo,  *2  50 

Spinning  and  Weaving  Calculations 8vo,  *s  oo 

Renwick,  W.  G.     Marble  and  Marble  Working 8vo,  5  oo 

Reynolds,   0.,   and  Idell,   F.   E.     Triple   Expansion  Engines.     (Science 

Series  No.  99.) i6mo,  o  50 

Rhead,  G.  F.     Simple  Structural  Woodwork i2mo,  *i  oo 

Rhodes,  H.  J.    Art  of  Lithography 8vo,  3  50 

Rice,  J.  M.,  and  Johnson,  W.  W.     A  New  Method  of  Obtaining  the  Differ- 
ential of  Functions i2mo,  o  50 

Richards,  W.  A.     Forging  of  Iron  and  Steel (In  Press.) 

Richards,  W.  A.,  and  North,  H.  B.    Manual  of  Cement  Testing. . .  .  i2mo,  *i  50 

Richardson,  J.     The  Modern  Steam  Engine 8vo,  *3  50 

Richardson,  S.  S.     Magnetism  and  Electricity I2mo,  *2  oo 

Rideal,  S.     Glue  and  Glue  Testing 8vo,  *4  oo 

Rimmer,  E.  J.    Boiler  Explosions,  Collapses  and  Mishaps 8vo,  *i  75 

Rings,  F.     Concrete  in  Theory  and  Practice i2mo,  *2  50 

Reinforced  Concrete  Bridges 4to,  *5  oo 

Ripper,  W.     Course  of  Instruction  in  Machine  Drawing folio,  *6  oo 

Roberts,  F.  C.     Figure  of  the  Earth.     (Science  Series  No.  79.) i6mo,  o  50 

Roberts,  J.,  Jr.     Laboratory  Work  in  Electrical  Engineering 8vo,  *2  oo 

Robertson,  L.  S.     Water-tube  Boilers .8vo,  2  oo 

Robinson,  J.  B.     Architectural  Composition 8vo,  *2  50 

Robinson,  S.  W.     Practical  Treatise  on  the  Teeth  of  Wheels.     (Science 

Series  No.  24.) i6mo,'  o  sc 

Railroad  Economics.     (Science  Series  No.  59.) i6mo,  o  53 

< Wrought  Iron  Bridge  Members.     (Science  Series  No.  60.) i6mo,  050 

Robson,  J.  H.     Machine  Drawing  and  Sketching 8vo,  *i  50 

Roebling,  J.  A.    Long  and  Short  Span  Railway  Bridges folio,  25  oo. 


24       D-  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Rogers,  A.  A  Laboratory  Guide  of  Industrial  Chemistry i2mo,  *i  50 

Rogers,  A.,  and  Aubert,  A.  B.  Industrial  Chemistry 8vo,  *5  QD 

Rogers,  F.  Magnetism  of  Iron  Vessels.  (Science  Series  No.  30.) .  i6mo,  o  So 
Rohland,  P.  Colloidal  and  Crystalloidal  State  of  Matter.  Trans,  by 

W.  J.  Britland  and  H.  E.  Potts 12010,  *i  25 

Rollins,  W.  Notes  on  X-Light 8vo,  *5  oo 

Rollinson,  C.  Alphabets Oblong,  i2mo,  *i  oo 

Rose,  J.  The  Pattern-makers'  Assistant 8vo,  2  50 

—  Key  to  Engines  and  Engine-running i2mo,  2  50 

Rose,  T.  K.  The  Precious  Metals.  (Westminster  Series.) 8vo,  *2  oo 

Rosenhain,  W.  Glass  Manufacture.  (Westminster  Series.) 8vo,  *2  oo 

Ross,  W.  A.  Blowpipe  in  Chemistry  and  Metallurgy I2mo,  *2  oo 

Roth.  Physical  Chemistry 8vo,  *2  oo 

Rouillion,  L.  The  Economics  of  Manual  Training 8vo,  2  oo 

Rowan,  F.  J.  Practical  Physics  of  the  Modern  Steam-boiler 8vo,  *s  oo 

and  Idell,  F.  E.  Boiler  Incrustation  and  Corrosion.  (Science 

Series  No.  27.) i6mo,  050 

Roxburgh,  W.  General  Foundry  Practice 8vo,  *3  50 

Ruhmer,  E.  Wireless  Telephony.  Trans,  by  J.  Erskine-Murray .  .  8vo,  *3  50 

Russell,  A.  Theory  of  Electric  Cables  and  Networks 8vo,  *3  oo 

Sabine,  R.     History  and  Progress  of  the  Electric  Telegraph i2mo,  i  25 

Saeltzer,  A.     Treatise  on  Acoustics i2mo,  i  oo 

Sanford,  P.  G.     Nitro-explosives 8vo,  *4  oo 

Saunders,  C.  H.     Handbook  of  Practical  Mechanics i6mo,  i  oo 

leather,  i  25 

Saunnier,   C.    Watchmaker's   Handbook i2mo,  3  oo 

Sayers,  H.  M.     Brakes  for  Tram  Cars 8vo,  *i  25 

Scheele,  C.  W.     Chemical  Essays 8vo,  *2  oo 

Scheithauer,    W.     Shale    Oils    and    Tars 8vo,  *3  5o 

Schellen,  H.     Magneto-electric  and  Dynamo-electric  Machines . . .  .8vo,  5  03 

Scherer,  R.     Casein.     Trans,  by  C.  Salter 8vc,  *3  oo 

SchicTDwitz,  P.     Rubber,  Its  Production  and  Industrial  Uses 8vo,  *3  oo 

Schindler,  K.     Iron  and  Steel  Construction  Works i2mo,  *i  25 

Schmall,  C.  N.    First  Course  in  Analytic  Geometry,  Plane  and  Solid. 

i2mo,  half  leather,  *i  75 

Schmall,  C.  N.,  and  Shack,  S.  M.     Elements  of  Plane  Geometry. . .  i2mo,  *i  25 

Sc1ameer,  L.     Flow  of  Water 8vo,  *3  or 

Schumann,  F.    A  Manual  of  Heating  and  Ventilation.  . .  .  i2mo,  leather,  i  50 

Schwarz,  E.  H.  L.    Causal  Geology 8vo,  *2  50 

Sdiweizer,  V.    Distillation  of  Resins 8vo,  *3  50 

Scott,  W.  W.     Qualitative  Analysis.    A  Laboratory  Manual 8vo,  *i  50 

Scribner,  J.  M.  Engineers'  and  Mechanics'  Companion.  .i6mo,  leather,  i  50 
Scudder,  H.j'  Electrical  Conductivity  and  lonization  Constants  of 

Organic  Compounds 8vo,  *3  oo 

Searle,  A.  B.     Modern  Brickmaking 8vo,  *s  oo 

—  Cement,   Concrete  and   Bricks 8vo,  *3  oo 

Searle,     G.    M.       "Sumners'     Method."      Condensed     and     Improved. 

(Science  Series   No.    124.) i6mo,  o  50 

Seaton,  A.  E.     Manual  of  Marine  Engineering 8vo  8  co 


D.  VAN  NOSTRAXD  CO.'S  SHORT  TITLE  CATALOG  25 

Seaton,  A.  E.,  and  Rounthwaite,  H.  M.     Pocket-book  of  Marine  Engi- 
neering   i6mo,  leather,  3  oo 

Seeligmann,  T.,  Torrilhon,  G.  L.,  and  Falconnet,  H.    India  Rubber  and 

Gutta  Percha.     Trans,  by  J.  G.  Mclntosh 8vo,  *s  oo 

Seidell,  A.    Solubilities  of  Inorganic  and  Organic  Substances 8vo,  *3  oo 

Sellew,  W.  H.     Steel  Rails 4to,  *i2  50 

Senter,  G.     Outlines  of  Physical  Chemistry i2mo,  *i  75 

Text-book  of  Inorganic  Chemistry i2mo,  *i  75 

Sever,  G.  F.    Electric  Engineering  Experiments 3vo,  boards,  *i  oo 

Sever,  G.  F.,  and  Townsend,  F.    Laboratory  and  Factory  Tests  in  Elec- 
trical Engineering 8vo,  *2  50 

Sewall,  C.  H.    Wireless  Telegraphy 8vo,  *2  oo 

Lessons  in  Telegraphy i2mo,  *i  oo 

Sewell,  T.    Elements  of  Electrical  Engineering 8vo,  *s  oo 

The  Construction  of  Dynamos 8vo,  *3  oo 

Sexton,  A.  H.    Fuel  and  Refractory  Materials izmo,  *2  50 

Chemistry  of  the  Materials  of  Engineering i2mo,  *2  50 

Alloys  (Non-Ferrous) 8vo,  *3  oo 

The  Metallurgy  of  Iron  and  Steel. 8vo,  *6  50 

Seymour,  A.     Practical  Lithography 8vo,  *2  50 

Modern  Printing  Inks 8vo,  *2  oo 

Shaw,  Henry  S.  H.    Mechanical  Integrators.    (Science  Series  No.  83.) 

i6mo,  o  50 

Shaw,  S.    History  of  the  Staffordshire  Potteries 8vo,  2  CD 

Chemistry  of  Compounds  Used  in  Porcelain  Manufacture. ..  .8vo,  *5  oo 

Shaw,  W.  N.     Forecasting  Weather 8vo,  *3  50 

Sheldon,  S.,  and  Hausmann,  E.    Direct  Current  Machines i2mo,  *2  50 

Alternating  Current  Machines i2mo,  *2  50 

Sheldon,  S.,  and  Hausmann,  E.     Electric  Traction  and  Transmission 

Engineering i2mo,  *2  50 

Sheriff,  F.  F.    Oil  Merchants'  Manual i2mo,  *3  50 

Shields,  J.  E.     Notes  on  Engineering  Construction i2mo,  i  50 

Shreve,  S.  H.    Strength  of  Bridges  and  Roofs 8vo,  3  50 

Shunk,  W.  F.     The  Field  Engineer i2mo,  morocco,  2  50 

Simmons,  W.  H.,  and  Appleton,  H.  A.    Handbook  of  Soap  Manufacture, 

8vo,  *3  oo 

Simmons,  W.  H.,  and  Mitchell,  C.  A.     Edible  Fats  and  Oils 8vo,  *3  oo 

Simms,  F.  W.    The  Principles  and  Practice  of  Levelling 8vo,  2  50 

Practical  Tunneling 8vo,  7  50 

Simpson,  G.     The  Naval  Constructor izmo,  morocco,  *5  oo 

Simpson,  W.     Foundations 8vo.   (In  Press.) 

Sinclair,  A.     Development  of  the  Locomotive  Engine. . .  8vo,  half  leather,  5  oo 

—  Twentieth  Century  Locomotive 8vo,  half  leather,  *$  oo 

Sindall,  R.  W.,  and  Bacon,  W.  N.     The  Testing  of  Wood  Pulp 8vo,  *2  50 

Sindall,  R.  W.    Manufacture  of  Paper.     (Westminster  Series.). ..  .8vo,  *2  oo 

Sloane,  T.  O'C.     Elementary  Electrical  Calculations i2mo,  *2  oo 

Smallwood,  J.  C.     Mechanical  Laboratory  Methods. ..  .i2mo,  leather,  *2  50 

Smith,  C.  A.  M.     Handbook  of  Testing,  MATERIALS 8vo,  *2  50 

Smith,  C.  A.  M.,  and  Warren,  A.  G.     New  Steam  Tables.  .  .  , 8vo,  *i  25; 


26       D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG 

Smith,  C.  F.     Practical  Alternating  Currants  and  Testing 8vo,  *2  50 

Practical  Testing  of  Dynamos  and  Motors 8vo,  *2  oo 

Smith,  F.  E.     Handbook  of  General  Instruction  for  Mechanics  .  .  .  i2mo,  i  50 

Smith,  H.  G.     Minerals  and  the  Microscope 

Smith,  J.  C.     Manufacture  of  Paint 8vo,  *3  or 

— —  Paint  and  Painting  Defects 

Smith,  R.  H.     Principles  of  Machine  Work i2mo,  *3  oo 

Elements  of  Machine  Work 121110,  *2  OD 

Smith,  W.     Chemistry  of  Hat  Manufacturing i2mo,  *3  oo 

Snell,    A.    T.     Electric    Motive  Power 8vo,  *4  oo 

Snow,  W.  G.     Pocketbook  of  Steam  Heating  and  Ventilation.    (In  Press.) 
Snow,  W.  G.,  and  Nolan,  T.     Ventilation  of  Buildings.     (Science  Series 

No.  5.) i6mo,  o  50 

Soddy,  F.     Radioactivity 8vo,  *3  oo 

Solomon,  M.     Electric  Lamps.     (Westminster  Series.) 8vo,  *2  oo 

Sothern,  J.  W.     The  Marine  Steam  Turbine 8vo,  *s  oo 

Verbal  Notes  and  Sketches  for  Marine  Engineers Cvo,  *5  oo 

Southcombe,  J.  E.     Chemistry  of  the  Oil  Industries.     (Outlines  of  In- 
dustrial Chemistry.) 8vo,  *3  oo 

Soxhlet,  D.  H.     Dyeing  and  Staining  Marble.     Trans,  by  A.  Morris  and 

H.  Robson 8vo,  *2  50 

Spang,  H.  W.     A  Practical  Treatise  on  Lightning  Protection i2mo,  i  oo 

Spangenburg,  L.    Fatigue  of  Metals.     Translated  by  S.   H.   Shreve. 

(Science  Series  No.  23.) i6mo,  o  50 

Specht,  G.  J.,  Hardy,  A.  S.,  McMaster,  J.  B.,  and  Walling.    Topographical 

Surveying.     (Science  Series  No.  72.) i6mo,  o  50 

Speyers,  C.  L.     Text-book  of  Physical  Chemistry 8vo,  *2  25 

Sprague,  E.  H.     Hydraulics ' i2mo,  i  25 

Stahl,  A.  W.     Transmission  of  Power.     (Science  Series  No.  28.)  .  i6m3, 

Stahl,  A.  W.,  and  Woods,  A.  T.    Elementary  Mechanism 12010,  *2  oo 

Staley,  C.,  and  Pierson,  G.  S.     The  Separate  System  of  Saw3ra33. .  .8^0,  *3  oo 

Standage,  H.  C.     Leatherworkers'  Manual 8vo,  *3  50 

Sealing  Waxes,  Wafers,  and  Other  Adhesives 8vo,  *2  oo 

Agglutinants  of  all  Kinds  for  all  Purposes i2mo,  *3  50 

Stanley,  H.    Practical  Applied  Physics (In  Press.) 

Stansbie,  J.  H.    Iron  and  Steel.     (Westminster  Series.) 8vo,  *2  o:> 

Steadman,  F.  M.     Unit  Photography  and  Actinometry (In  Press.) 

Stecher,  G.  E.     Cork.    Its  Origin  and  Industrial  Uses i2mo,  i  oo 

Steinman,  D.  B.     Suspension  Bridges  and  Cantilevers.     (Science  Series 

No.  127.) o  50 

Stevens,  H.  P.     Paper  Mill  Chemist i6mo,  *2  50 

Stevens,  J.  S.     Precision  of  Measurements (In  Press.) 

Stevenson,  J.  L.     Blast-Furnace  Calculations i2mo,  leather,  *2  oo 

Stewart,  A.     Modern  Polyphase  Machinery i2mo,  *2  oo 

Stewart,  G.     Modern  Steam  Traps 12010,  *i  25 

Stiles,  A.     Tables  for  Field  Engineers i2mo,  i  oo 

Stillman,  P.     Steam-engine  Indicator i2mo,  i  oo 

Stodola,  A.    Steam  Turbines.    Trans,  by  L.  C.  Loewenstein 8vo,  *5  oo 

Stone,  H.    The  Timbers  of  Commerce 8vo,  3  50 

Stone,  Gen.  R.    New  Roads  and  Road  Laws i2mo,  i  oo 


D.  VAN  NOSTRAND  CO.'S  SHORT  TITLE  CATALOG  27 

Stopes,  M.     Ancient  Plants 8vo,  *2  oo 

The  Study  of  Plant  Life 8vo,  *2  oo 

Stumpf ,  Prof.     Una-Flow  of  Steam  Engine 4to,  *3  50 

Sudborough,  J.  J.,  and  James,  T.  C.    Practical  Organic  Chemistry..  i2ma,  *2  oo 

Suffling,  E.  R.     Treatise  on  the  Art  of  Glass  Painting 8vo,  *3  50 

Swan,  K.     Patents,  Designs  and  Trade  Marks.     (Westminster  Series.). 

8vo,  *2  oo 
Swinburne,  J.,  Wordingham,  C.  H.,  and  Martin,  T.  C.     Electric  Currents. 

(Science  Series  No.  109.) i6mo,  o  50 

Swoope,  C.  W.     Lessons  in  Practical  Electricity i2mo,  *2  oo 

Tailfer,  L.     Bleaching  Linen  and  Cotton  Yarn  and  Fabrics 8vo,  *5  oo 

Tate,  J.  S.     Surcharged  and  Different  Forms  of  Retaining- walls.    (Science 

Series  No.  7.) i6mo,  o  50 

Taylor,  E.  N.     Small  Water  Supplies , i2mo,  *2  oo 

Templeton,  W.     Practical  Mechanic's  Workshop  Companion. 

i2mo,  morocco,  2  oo 
Terry,  H.  L.    India  Rubber  and  its  Manufacture.     (Westminster  Series.) 

8vo,  *2  oo 
Thayer,  H.  R.     Structural  Design.    8vo. 

Vol.     I.     Elements  of  Structural  Design *2  oo 

Vol.    II.     Design  of  Simple  Structures (In  Preparation.) 

Vol.  III.    Design  of  Advanced  Structures (In  Preparation.) 

Thiess,  J.  B.,  and  Joy,  G.  A.     Toll  Telephone  Practice 8vo,  *3  50 

Thorn,  C.,  and  Jones,  W.  H.     Telegraphic  Connections..  .  .oblong,  i2mo,  150 

Thomas,  C.  W.     Paper-makers'  Handbook (In  Press.) 

Thompson,  A.  B.     Oil  Fields  of  Russia 4to,  *7  50 

Petroleum  Mining  and  Oil  Field  Development 8vo,  *5  oo 

Thompson,  S.  P.     Dynamo  Electric  Machines.     (Science  Series  No.  75.) 

i6mo,  o  So 

Thompson,  W.  P.     Handbook  of  Patent  Law  of  All  Countries i6mo,  i  50 

Thomson,  G.  S.     Milk  and  Cream  Testing i2mo,  *i  75 

—  Modern  Sanitary  Engineering,  House  Drainage,  etc 8vo,  *3  oo 

Thornley,  T.     Cotton  Combing  Machines 8vo,  *3  oo 

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Turrill,  S.  M.    Elementary  Course  in  Perspective 121110,  *i  25 

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Walker,  F.     Aerial  Navigation 8vo,  2  co 

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Winchell,  N.  H.,  and  A.  N.    Elements  of  Optical  Mineralogy 8vo,  *3  50 

Winkler,  C.,  and  Lunge,  G.    Handbook  of  Technical  Gas-Analysis.  .8vo,  4  oo 

Winslow,  A.    Stadia  Surveying.     (Science  Series  No.  77.) i6mo,  o  50 

Wisser,  Lieut.  J.  P.     Explosive  Materials.     (Science  Series  No.  70.) 

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Wood,  De  V.    Luminiferous  Aether.     (Science  Series  No.  8s)...i6mo,  o  50 
Wood,  J.  K.     Chemistry  of  Dyeing.      (Chemical  Monographs  No.  2.) 

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Worden,  E.  C.     The  Nitrocellulose  Industry.    Two  Volumes 8vo,  *io  oo 

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Wren,  H.    Organometallic  Compounds  of  Zinc  and  Magnesium.    (Chem- 
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Wright,  A.  C.    Analysis  of  Oils  and  Allied  Substances 8vo,  *s  50 

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Wright,  F.  W.     Design  of  a   Condensing  Plant i2mo,  *i  50 . 

Wright,  H.   E.     Handy  Book  for  Brewers 8vo,  *5  oo 

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Wright,  T.  W.     Elements  of  Mechanics 8vo,  *2  50 

Wright,  T.  W.,  and  Hayf ord,  J.  F.    Adjustment  of  Observations .  . .  8vo,  *3  oa 

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Zahner,  R.    Transmission  of  Power.     (Science  Series  No.  40.)-.i6mo, 

Zeidler,  J.,  and  Lustgarten,  J.     Electric  Arc  Lamps 8vo,  *2  oo 

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Zimmer,  G.  F.     Mechanical  Handling  of  Material 4*0,  *io  oo 

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